Make core::ops::Place an unsafe trait

Consumers of `Place` would reasonably expect that the `pointer` function returns a valid pointer to memory that can actually be written to.

Expose float from_bits and to_bits in libcore.

These methods have no dependencies on libm and thus should be offered in libcore.

Immovable generators

This adds support for immovable generators which allow you to borrow local values inside generator across suspension points. These are declared using a `static` keyword:
```rust
let mut generator = static || {
    let local = &Vec::new();
    yield;
    local.push(0i8);
};
generator.resume();

// ERROR moving the generator after it has resumed would invalidate the interior reference
// drop(generator);
```

Region inference is no longer affected by the types stored in generators so the regions inside should be similar to other code (and unaffected by the presence of `yield` expressions). The borrow checker is extended to pick up the slack so interior references still result in errors for movable generators. This fixes #44197, #45259 and #45093.

This PR depends on [PR #44917 (immovable types)](https://github.com/rust-lang/rust/pull/44917), I suggest potential reviewers ignore the first commit as it adds immovable types.

Rollup of 14 pull requests

- Successful merges: #47423, #47425, #47440, #47541, #47549, #47554, #47558, #47610, #47635, #47655, #47661, #47662, #47667, #47672
- Failed merges:

rustdoc: Show when traits are auto traits

Fix quoted search

r? @QuietMisdreavus

Add dynamic-drop test to nll tests also

r? @nikomatsakis

Fixes #47585

Inline some rustc_driver function

Fix spurious warning on empty proc macro crates

While attempting to reproduce rust-lang/rust#47086 I noticed the following warning:

```shell
> rustc /dev/null --crate-type proc-macro
warning: unused variable: `registrar`
 --> /dev/null:0:1
```

As there are no macros to register the automatically generated registrar function for the crate has no body. As a result its `registrar` argument is unused triggering the above warning.

The warning is confusing and not easily actionable by the developer. It could also be triggered legitimately by e.g. having all of the macros in a crate #[cfg]'ed out.

Fix by naming the generated argument `_registrar` inside `mk_registrar()`. This suppresses the unused variable warning.

Remove the IGNORED_ATTR_NAMES thread local

Multiple themes for rustdoc

r? @QuietMisdreavus

LLVM5: Update DW_OP_plus to DW_OP_plus_uconst

LLVM <= 4.0 used a non-standard interpretation of `DW_OP_plus`.  In the
DWARF standard, this adds two items on the expressions stack.  LLVM's
behavior was more like DWARF's `DW_OP_plus_uconst` -- adding a constant
that follows the op.  The patch series starting with [D33892] switched
to the standard DWARF interpretation, so we need to follow.

[D33892]: https://reviews.llvm.org/D33892

Fixes #47464
r? @EddyB

Add rustc-args option to test runner

r? @nikomatsakis

Make liballoc_jemalloc work on CloudABI.

The automated builds for CloudABI in dist-various-2 don't use
--disable-jemalloc, even though my original container image did. Instead
of setting that flag, let's go the extra mile of making jemalloc work.
CloudABI's C library already uses jemalloc and now exposes the API
extensions used by us.

This makes the CloudABI dist work out of the box.

Add regression test for #29723

cc #29723

r? @nikomatsakis

Fixes sparc64 cabi fixes.

Argument up to 16 bytes size is provided in registers.
Return value up to 32 bytes size is stored in registers.

Fixes: #46679

---

Firefox now (almost) build on sparc. Original rust issue seems to be gone. Note that I'm not rust expert and the fix was suggested in bug.

Change the --unpretty flag to -Z unpretty

First PR 😄 !

-Z unpretty no longer requires -Z unstable-options.

Also, I mildly changed the syntax of the flag to match the other -Z flags. All uses of the flag take the form `unpretty=something` where something can either `string` or `string=string` (see the help messages of the CLI).

Fix #47395

r? @nikomatsakis EDIT: apparently rust-highfive doesn't see edits...

Properly pass down immutability info for thread-locals.

For thread-locals we call into cat_rvalue_node() to create a CMT
(Category, Mutability, Type) that always has McDeclared. This is
incorrect for thread-locals that don't have the 'mut' keyword; we should
use McImmutable there.

Extend cat_rvalue_node() to have an additional mutability parameter. Fix
up all the callers to make use of that function. Also extend one of the
existing unit tests to cover this.

Fixes: #47053

Check for deadlinks from the summary during book generation

Previously, any deadlinks from a book's SUMMARY.md wouldn't
cause any errors or warnings or similar but mdbook would simply
create a page with blank content.

This has kept bug #47394 hidden. It should have been detected
back in the PR when those wrongly named files got added to the
book.

PR #47414 was one component of the solution. This change
is a second line of defense for the unstable book and a first
line of defense for any other book.

We also update mdbook to the most recent version.

Auto merge of #47046 - Manishearth:intra-doc-links, r=eddyb,GuillaumeGomez,QuietMisdreavus,Manishearth

Implement RFC 1946 - intra-rustdoc links

https://github.com/rust-lang/rfcs/pull/1946 https://github.com/rust-lang/rust/issues/43466

Note for reviewers: The plain line counts are a little inflated because of how the markdown link parsing was done. [Read the file diff with "whitespace only" changes removed](https://github.com/rust-lang/rust/pull/47046/files?w=1) to get a better view of what actually changed there.

This pulls the name/path resolution mechanisms out of the compiler and runs it on the markdown in a crate's docs, so that links can be made to `SomeStruct` directly rather than finding the folder path to `struct.SomeStruct.html`. Check the `src/test/rustdoc/intra-paths.rs` test in this PR for a demo. The change was... a little invasive, but unlocks a really powerful mechanism for writing documentation that doesn't care about where an item was written to on the hard disk.

Items included:

 - [x] Make work with the hoedown renderer
 - [x] Handle relative paths
 - [x] Parse out the "path ambiguities" qualifiers (`[crate foo]`, `[struct Foo]`, `[foo()]`, `[static FOO]`, `[foo!]`, etc)
 - [x] Resolve foreign macros
 - [x] Resolve local macros
 - [x] Handle the use of inner/outer attributes giving different resolution scopes (handling for non-modules pushed to different PR)

Items not included:

 - [ ] Make sure cross-crate inlining works (blocked on refactor described in https://github.com/rust-lang/rust/pull/47046#issuecomment-354824520)
 - [ ] Implied Shortcut Reference Links (where just doing `[::std::iter::Iterator][]` without a reference anchor will resolve using the reference name rather than the link target) (requires modifying the markdown parser - blocked on Hoedown/Pulldown switch and https://github.com/google/pulldown-cmark/issues/121)
 - [ ] Handle enum variants and UFCS methods (Enum variants link to the enum page, associated methods don't link at all)
 - [ ] Emit more warnings/errors when things fail to resolve (linking to a value-namespaced item without a qualifier will emit an error, otherwise the link is just treated as a url, not a rust path)
 - [ ] Give better spans for resolution errors (currently the span for the first doc comment is used)
 - [ ] Check for inner doc comments on things that aren't modules

I'm making the PR, but it should be noted that most of the work was done by Misdreavus 😄

(Editor's note: This has become a lie, check that commit log, Manish did a ton of work after this PR was opened `>_>`)

Adds support for immovable generators. Move checking of invalid borrows across suspension points to borrowck. Fixes #44197, #45259 and #45093.

[Incremental] Cache hashes for AdDef and ty::Slice<T>

r? @michaelwoerister

rustc: Lower link args to `@`-files on Windows more

When spawning a linker rustc has historically been known to blow OS limits for
the command line being too large, notably on Windows. This is especially true of
incremental compilation where there can be dozens of object files per
compilation. The compiler currently has logic for detecting a failure to spawn
and instead passing arguments via a file instead, but this failure detection
only triggers if a process actually fails to spawn.

Unfortunately on Windows we've got something else to worry about which is
`cmd.exe`. The compiler may be running a linker through `cmd.exe` where
`cmd.exe` has a limit of 8192 on the command line vs 32k on `CreateProcess`.
Moreso rustc actually succeeds in spawning `cmd.exe` today, it's just that after
it's running `cmd.exe` fails to spawn its child, which rustc doesn't currently
detect.

Consequently this commit updates the logic for the spawning the linker on
Windows to instead have a heuristic to see if we need to pass arguments via a
file. This heuristic is an overly pessimistic and "inaccurate" calculation which
just calls `len` on a bunch of `OsString` instances (where `len` is not
precisely the length in u16 elements). This number, when exceeding the 6k
threshold, will force rustc to always pass arguments through a file.

This strategy should avoid us trying to parse the output on Windows of the
linker to see if it successfully spawned yet failed to actually sub-spawn the
linker. We may just be passing arguments through files a little more commonly
now...

The motivation for this commit was a recent bug in Gecko [1] when beta testing,
notably when incremental compilation was enabled it blew out the limit on
`cmd.exe`. This commit will also fix #46999 as well though as emscripten uses a
bat script as well (and we're blowing the limit there).

[1]: https://bugzilla.mozilla.org/show_bug.cgi?id=1430886

Closes #46999

renumber regions in generators

This fixes #47189, but I think we still have to double check various things around how to treat generators in MIR type check + borrow check (e.g., what borrows should be invalidated by a `Suspend`? What consistency properties should type check be enforcing anyway around the "interior" type?)

Also fixes #47587 thanks to @spastorino's commit.

r? @pnkfelix