Rollup of 11 pull requests

- Successful merges: #32403, #32596, #32675, #32678, #32685, #32686, #32692, #32710, #32712, #32714, #32715
- Failed merges: #32488

trans: don't declare symbols that were already imported.

Fixes #32740 by checking for a declaration before attempting a new one.
Before, `LLVMGetOrInsertFunction` was called for a existing import, but with a different type.
The returned value was a cast function pointer instead of a declaration, and we gave this
value to `llvm::SetFunctionCallConv` & friends , which triggered an LLVM assertion.

rustdoc: factor out function for getting inner html of highlighted source

JSON errors: give better spans for SpanEnd errors

Autoderef when suggesting to call `(self.field)`

Fixes #32128

Fix "consider removing this semicolon" help

Check last statement in a block, not the first.

Example of current weirdness: http://is.gd/w80J9h

The help was only rarely emitted, and if so, often incorrectly (see above playpen). It was basically only useful with single-statement functions.

Inline Duration constructors and accessors

These are all super small functions

r? @alexcrichton

Prefix jemalloc on DragonFly to prevent segfaults.

Similar to commits ed015456 (iOS)
and e3b414d8 (Android)

adding freebsd i686 snapshot 4d3eebff

@alexcrichton will you please upload the following file when landing this patch:

https://github.com/dhuseby/rust-manual-snapshots/raw/master/rust-stage0-2016-02-17-4d3eebf-freebsd-i386-4e2af0b34eb335e173aebff543be693724a956c2.tar.bz2

rustdoc: make rustdoc less pass-aware

Instead of hardcoding knowledge about the strip-private pass into the
rendering process we represent (some) stripped items as `ItemEnum::StrippedItem`.

Rustdoc will, for example, generate redirect pages for public items
contained in private modules which have been re-exported to somewhere
externally reachable - this will now not only work for the `strip-private`
pass, but for other passes as well, such as the `strip-hidden` pass.

r? @alexcrichton

adds dragonflybsd to snapshots.txt

@alexcrichton please upload the following snapshots when landing this patch:

https://github.com/dhuseby/rust-manual-snapshots/raw/master/rust-stage0-2016-02-17-4d3eebf-dragonfly-x86_64-765bb5820ad406e966ec0ac51c8070b656459b02.tar.bz2

https://github.com/dhuseby/rust-manual-snapshots/raw/master/rust-stage0-2016-02-17-4d3eebf-freebsd-x86_64-395adf223f3f25514c9dffecb524f493c42a0e5d.tar.bz2

Plumb obligations through librustc/infer

Like #32542, but more like #31867.

TODO before merge: make an issue for the propagation of obligations through... uh, everywhere... then replace the `#????`s with the actual issue number.

cc @jroesch
r? @nikomatsakis

Fix issue: Global paths in `use` directives can begin with `super` or `self` #32225

This PR fixes #32225 by warning on `use ::super::...` and `use ::self::...` on `resolve`.

Current changes is the most minimal and ad-hoc.

Remove implicit binder from `FnSpace` in `VecPerParamSpace` (fixes #20526)

This removes the implicit binder from `FnSpace` in `VecPerParamSpace` so that `Binder<T>` is the only region binder (as described in issue #20526), and refactors away `enter_region_binder` and `exit_region_binder` from `TypeFolder`.

Issue: #32225

resolve: Improve import failure detection and lay groundwork for RFC 1422

This PR improves import failure detection and lays some groundwork for RFC 1422.
More specifically, it
 - Avoids recomputing the resolution of an import directive's module path.
 - Refactors code in `resolve_imports` that does not scale to the arbitrarily many levels of visibility that will be required by RFC 1422.
  - Replaces `ModuleS`'s fields `public_glob_count`, `private_glob_count`, and `resolved_globs` with a list of glob import directives `globs`.
  - Replaces `NameResolution`'s fields `pub_outstanding_references` and `outstanding_references` with a field `single_imports` of a newly defined type `SingleImports`.
 - Improves import failure detection by detecting cycles that include single imports (currently, only cycles of globs are detected). This fixes #32119.

r? @nikomatsakis

Only allow using the atomic intrinsics on integer types

Using these with non-integer types results in LLVM asserts. Atomic operations on non-integer types will require values be transmuted into an integer type of suitable size.

This doesn't affect the standard library since `AtomicBool` and `AtomicPtr` currently use `usize` for atomic operations.

r? @EddyB

process cycles as soon as they are detected

We used to wait for the recursion limit, but that might well be too
long!

Fixes #32326
r? @aturon

When deciding on a coinductive match, we were examining the new
obligation and the backtrace, but not the *current* obligation that goes
in between the two.  Refactoring the code to just have the cycle given
as input also made things a lot simpler.

We used to wait for the recursion limit, but that might well be too
long!

check constants even if they are not used in the current crate

For now this is just a `warn`-by-default lint. I suggest to make it a `deny`-by-default lint in the next release cycle (so no dependencies break), and then in another release cycle move to an error.

cc #19265
cc #3170

add missing spaces in #16758 warning

I should probably add a test.

Fixes #32128

Check last statement in a block, not the first

Fix a couple of dead links on core::num::ParseFloatError docs

rBreak Critical Edges and other MIR work

This PR is built on top of #32080.

This adds the basic depth-first traversals for MIR, preorder, postorder and reverse postorder. The MIR blocks are now translated using reverse postorder. There is also a transform for breaking critical edges, which includes the edges from `invoke`d calls (`Drop` and `Call`), to account for the fact that we can't add code after an `invoke`. It also stops generating the intermediate block (since the transform essentially does it if necessary already).

The kinds of cases this deals with are difficult to produce, so the test is the one I managed to get. However, it seems to bootstrap with `-Z orbit`, which it didn't before my changes.

mk: Add configure option for disabling codegen tests

Our `codegen` test suite requires the LLVM `FileCheck` utility but unfortunately
this isn't always available in all custom LLVM roots (e.g. those specified via
`--llvm-root`). This commit adds a `./configure` option called
`--disable-codegen-tests` which will manually disable running these tests. In
the case that this option is passed we can forgo the need for the `FileCheck`
executable. Note that we still require `FileCheck` by default as we will attempt
to run these tests.

Closes #28667