Fix erroneous reference to Arc instead of Rc in rc::Weak documentation

The docs for `rc::Weak` refer to `Arc` in one place, where they should obviously be referring to `Rc`; presumably this was erroneously copied over from the `arc::Weak` docs.

redox: handle multiple paths in PATH

`std::time::Duration`: improve _precision_ of terminology in docs

Changed wording of docs on `std::time::Duration` for better clarity w.r.t. the contents of the type and the purpose of its methods.  (Specifically, removed the use of the word "precision" to describe the fractional part of the `Duration` because "precision" is more properly used to describe how _precise_ a value is, i.e. its granularity in this case.)

Workaround "Quasi-quoting is inefficient" warning in incremental rustbuild introduced in #43252.

After #43252 is merged, building stage0 libcore with `-i` (`--incremental`) flag will cause 17 "Quasi-quoting might make incremental compilation very inefficient: NtExpr(..)" warnings, as in #40946.

```
warning: Quasi-quoting might make incremental compilation very inefficient: NtExpr(..)
   --> src/libcore/default.rs:133:21
    |
133 |             #[doc = $doc]
    |                     ^^^^
...
139 | default_impl! { (), (), "Returns the default value of `()`" }
    | ------------------------------------------------------------- in this macro invocation
(× 17)
```

True fix for #40946 will take at least 12 weeks from now to make into the next stage0, so it is quicker to workaround it in libcore instead.

cc @vbrandl @jseyfried

libstd: remove redundant & from &Path::new(...)

```rust
fn Path::new<S: AsRef ...>(s: &S) -> &Path
```

* https://doc.rust-lang.org/std/path/struct.Path.html#method.new

Change Travis CI job order.

Reorder the job matrix to take advantage of the order how Travis CI starts them in rust-lang/rust. Plus other refactoring of `.travis.yml`.

1. Move the `$ALLOW_PR` image to the top, so pull requests will start testing as immediately after the build is started. Previously the `$ALLOW_PR` image starts 6 minutes after the build was scheduled.

2. Move the slow macOS images near the top, so they share more time with the rest of the faster Linux builds, which should shorten total test time (actually not much, about 7 minutes at most if this change does work).

3. Merged the `install` section of both Linux and macOS to make the `env:` section a bit shorter, and enable change 4 below.

4. Do not download or install anything if `$SKIP_BUILD == true`, which further reduces chance of spurious failure in the PR-CI stage (avoid the red cross appearing even if CI passed).

(IMO `$SKIP_BUILD` should not even exist: those irrelevant jobs should not start at all, but that would require travis-ci/travis-ci#2778 which has been rejected)

Update merge queue link in CONTRIBUTING.md

Update docs on Error struct. #29355

This adds a pretty contrived example of the usage of fmt::Error. I am
very open to suggestions for a better one.

I have also highlighted the fmt::Error vs std::error::Error.

r? @steveklabnik

Support generic lifetime arguments in method calls

Fixes https://github.com/rust-lang/rust/issues/42403
Fixes https://github.com/rust-lang/rust/issues/42115
Lifetimes in a method call `x.f::<'a, 'b, T, U>()` are treated exactly like lifetimes in the equivalent UFCS call `X::f::<'a, 'b, T, U>`.
In addition, if the method has late bound lifetime parameters (explicit or implicit), then explicitly specifying lifetime arguments is not permitted (guarded by a compatibility lint).
[breaking-change] because previously lifetimes in method calls were accepted unconditionally.

r? @EddyB

Reorder the job matrix to take advantage of the order how Travis CI starts
them in rust-lang/rust. Plus other refactoring of `.travis.yml`.

1. Move the `$ALLOW_PR` image to the top, so users' PRs will start testing
   immediately. Previously the `$ALLOW_PR` image starts 6 minutes after the
   build was scheduled.

2. Move the slow macOS images near the top, so they share more time with
   the rest of the faster Linux builds, which should shorten total test
   time (actually not much, about 7 minutes at most if this change does
   work).

3. Merged the `install` section of both Linux and macOS to make the `env:`
   section a bit shorter, and enable change 4 below.

4. Do not download or install anything if `$SKIP_BUILD == true`, which
   further reduces chance of spurious failure in the PR-CI stage (avoid the
   red cross appearing even if CI passed).

travis: Make a few `curl` invocations more resilient

Use the `-f` flag to indicate that, for example, a 500 response code is to be
considered a failure, triggering the normal retry logic. Also ignore errors
where we check the date from google.com, as a failure there shouldn't fail the
build.

Use the `-f` flag to indicate that, for example, a 500 response code is to be
considered a failure, triggering the normal retry logic. Also ignore errors
where we check the date from google.com, as a failure there shouldn't fail the
build.

Fix treatment of lifetimes defined in nested types during detection of late bound regions in signatures.
Do not replace substs with inference variables when "cannot specify lifetime arguments explicitly..." is reported as a lint.

Changed wording of docs on `std::time::Duration` for better clarity
w.r.t. the contents of the type and the purpose of its methods.

After #43252 is merged, building stage0 libcore with -i (--incremental)
flag will cause 17 "Quasi-quoting might make incremental compilation very
inefficient: NtExpr(..)" warnings, as in #40946.

Fixing the warning in #40946 will take 12 weeks from now to make into the
next stage0, so it is quicker to workaround it in libcore instead.

Add support for dylibs with Address Sanitizer

Many applications use address sanitizer to assert correct behaviour of their programs. When using Rust with C, it's much more important to assert correct programs with tools like asan/lsan due to the unsafe nature of the access across an ffi boundary. However, previously only rust bin types could use asan. This posed a challenge for existing C applications that link or dlopen .so when the C application is compiled with asan.

This PR enables asan to be linked to the dylib and cdylib crate type. We alter the test to check the proc-macro crate does not work with -Z sanitizer=address. Finally, we add a test that compiles a shared object in rust, then another rust program links it and demonstrates a crash through the call to the library.

This PR is nearly complete, but I do require advice on the change to fix the -lasan that currently exists in the dylib test. This is required because the link statement is not being added correctly to the rustc build when -Z sanitizer=address is added (and I'm not 100% sure why)

Thanks,

fn Path::new<S: AsRef ...>(s: &S) -> &Path
Signed-off-by: NNODA, Kai <nodakai@gmail.com>

Fix `range_covered_by_constructor` for exclusive ranges.

This resolves #43253

Change some notes into suggestions

r? @petrochenkov since you commented on the same edits in #39458

The produced paths aren't stable between builds, since
reporting paths inside resolve, before resolve is finished
might produce paths resolved to type aliases instead of
the concrete type.

Compile-fail tests can match just parts of messages, so they
don't "suffer" from this issue.

This is just a workaround, the instability should be fixed
in the future.

More Rust/RLS integration

r? @alexcrichton

cc https://github.com/rust-lang-nursery/rls/issues/310

closes #41199
closes #41197

Compile `compiler_builtins` with `abort` panic strategy

A workaround for https://github.com/rust-lang/rust/issues/43095

In case this causes unexpected consequences, I use a simpler workaround locally:
```diff
--- a/src/bootstrap/bin/rustc.rs
+++ b/src/bootstrap/bin/rustc.rs
@@ -175,7 +175,9 @@ fn main() {
         }

         if let Ok(s) = env::var("RUSTC_CODEGEN_UNITS") {
-            cmd.arg("-C").arg(format!("codegen-units={}", s));
+            if crate_name != "compiler_builtins" {
+                cmd.arg("-C").arg(format!("codegen-units={}", s));
+            }
         }

         // Emit save-analysis info.
```

r? @alexcrichton

Stabilize float_bits_conv for Rust 1.21

Stabilizes the `float_bits_conv` lib feature for the 1.20 release of Rust. I've initially implemented the feature in #39271 and later made PR #43025 to output quiet NaNs even on platforms with different encodings, which seems to have been the only unresolved issue of the API.

Due to PR #43025 being only applied to master this stabilisation can't happen for Rust 1.19 through the usual "stabilisation on beta" system that is being done for library APIs.

r? @BurntSushi

closes #40470.

This resolves #43253

add u128/i128 to sum/product implementors

Resolves #43235.

Document default values for primitive types

All primitive types implement the `Default` trait but the documentation just says `Returns the "default value" for a type.` and doesn't give a hint about the actual default value. I think it would be good to document the default values in a proper way.
I changed the `default_impl` macro to accept a doc string as a third parameter and use this string to overwrite the documentation of `default()` for each primitive type.
The generated documentation now looks like this:
![Documentation of default() on the bool primitive](https://i.imgur.com/nK6TApo.png)

macros: fix regression involving identifiers in `macro_rules!` patterns.

Fixes #42019.
r? @nrc