std: minor whitespace cleanup
syntax: Allow syntax extensions to have attributes
syntax: add syntax extension helper to make simple view items
auto merge of #12421 : Hywan/rust/api_doc, r=alexcrichton

I was reading the code and saw this. Not the best contribution of my life ;-).
std: rewrite Hash to make it more generic

This patch merges IterBytes and Hash traits, which clears up the
confusion of using `#[deriving(IterBytes)]` to support hashing.
Instead, it now is much easier to use the new `#[deriving(Hash)]`
for making a type hashable with a stream hash.

Furthermore, it supports custom non-stream-based hashers, such as
if a value's hash was cached in a database.

This does not yet replace the old IterBytes-hash with this new
version.
remove the TyDesc from TypedArena

This prevents generating visit glue when using a TypedArena. The problem
still exists for the untyped Arena.
test: 'ratcher' is not a word
auto merge of #12422 : alexcrichton/rust/buffered-default, r=brson

One of the most common ways to use the stdin stream is to read it line by line
for a small program. In order to facilitate this common usage pattern, this
commit changes the stdin() function to return a BufferedReader by default. A new
`stdin_raw()` method was added to get access to the raw unbuffered stream.

I have not changed the stdout or stderr methods because they are currently
unable to flush in their destructor, but #12403 should have just fixed that.
Restore LLVM to the correct revision

PR #12407 was accidentally reverted by PR #12411. Restore the correct
version of LLVM that PR #12407 introduced.
auto merge of #12462 : kballard/rust/restore-llvm-from-12407, r=brson

PR #12407 was accidentally reverted by PR #12411. Restore the correct
version of LLVM that PR #12407 introduced.
mk: restore check-notidy.

tidy has some limitations (e.g. the "checked in binaries" check doesn't
and can't actually check git), and so it's useful to run tests without
running tidy occasionally.
auto merge of #12427 : alexcrichton/rust/snapshots, r=brson

This contains the fix for #4252 so we can start using methods in destructors.
auto merge of #12433 : alexcrichton/rust/fix-some-config-things, r=brson

These are mostly centered around using an external LLVM (notably 3.5)
auto merge of #12437 : alexcrichton/rust/travis-yml, r=brson

Travis CI provides an easy-to-use continuous integration infrastructure for
github repos to use. Travis will automatically test all PRs which are opened
against the rust repository, informing PR owners of the test results.

I believe that this will be a very convenient piece of infrastructure as we'll
be able to reduce the load on bors quite a bit. In theory all PRs opened have
had the full test suite run against them, but unfortunately this is rarely the
case (I'm a prime suspect). Travis will be able to provide easy and relatively
quick (~30min) feedback for PRs. By ensuring fewer failures on bors, we can
hopefully feed more successful jobs to bors.

Overall, I expect this to be very helpful for new contributors as well as
regular contributors as it's another layer of tests being run which will
hopefully catch things sooner. One of the most convenient parts about using
Travis is that there's very little burden in terms of maintenance, and if things
go wrong we can easily turn travis completely off.

Note that this is *not* the metric by which a PR will be merged with. Using
travis will purely be another source for running tests, we will continue to gate
all PRs on bors.
Warn about unnecessary parentheses upon assignment

Closes #12366.

Parentheses around assignment statements such as

    let mut a = (0);
    a = (1);
    a += (2);

are not necessary and therefore an unnecessary_parens warning is raised when
statements like this occur.

The warning mechanism was refactored along the way to allow for code reuse
between the routines for checking expressions and statements.

Code had to be adopted throughout the compiler and standard libraries to comply
with this modification of the lint.
auto merge of #12439 : cmr/rust/rustdoc-reset, r=thestinger

rustdoc: web: don't reset the search bar
auto merge of #12441 : kud1ing/rust/backticks, r=brson

Not all of those messages are covered by tests. I am not sure how to trigger them and where to put those tests.

Also some message patterns in the existing tests are not complete.
For example, i find `error: mismatched types: expected "i32" but found "char" (expected i32 but found char)` a bit repetitive, but as i can see there is no test covering that.
Fix emacs indentation of multi-line match patterns

Aligns to the same column if the previous line ends in a single '|' (but
not a '||').
auto merge of #12366 : aepsil0n/rust/feature/unnecessary_parens_around_assigned_values, r=alexcrichton

Fixes #12350.

Parentheses around assignment statements such as

```rust
let mut a = (0);
a = (1);
a += (2);
```

are not necessary and therefore an unnecessary_parens warning is raised when
statements like this occur.

NOTE: In `let` declarations this does not work as intended. Is it possible that they do not count as assignment expressions (`ExprAssign`)? (edit: this is fixed by now)

Furthermore, there are some cases that I fixed in the rest of the code, where parentheses could potentially enhance readability. Compare these lines:

```rust
a = b == c;
a = (b == c);
```

Thus, after having worked on this I'm not entirely sure, whether we should go through with this patch or not. Probably a matter of debate. ;)
Force all lang items to be reachable

This prevents linker errors as found in #11591

Closes #11591