rust.md : update crate attributes.

#[ author = "Jane Doe" ]; raises "warning: unknown crate attribute"
Add method .as_mut_slice() to MutableVector

This method is primarily intended to allow for converting a [T, ..N] to
a &mut [T].
Rename pkgid variables
Rename PkgId to CrateId
Rename uses of PkgId to CrateId in librustpkg
Update Docs to use crateid
Register new snapshots.
Fix a deadlock in a libgreen test

Turns out when you grab an OS mutex, you need to be careful about when and where
things are scheduled!
auto merge of #11204 : alexcrichton/rust/issue-11200, r=cmr

Turns out when you grab an OS mutex, you need to be careful about when and where
things are scheduled!

I've confirmed that I could fairly reliably get a deadlock (1 in 100 times ish) before this, and I cannot get a deadlock after this (after 1000+ runs).

Closes #11200
Update llvm.
auto merge of #11181 : luqmana/rust/up-llvm, r=alexcrichton

No longer need to handle GNUEABIHF and hard floats since LLVM should now choose the right default. Fixes #11164.
rustdoc: only filter lines starting with '# ' from the shown code.

Currently any line starting with `#` is filtered from the output,
including line like `#[deriving]`; this patch makes it so lines are only
filtered when followed by a space similar to the current behaviour of
the tutorial/manual tester.
rustdoc: Unify the handling of the hidden example lines.
auto merge of #11168 : sfackler/rust/de-at-extctxt, r=alexcrichton

* Pass `&ExtCtxt` instead of `@ExtCtxt`.
* Stop passing duplicate parameters around in `expand`.
* Make `ast_fold` methods take `&mut self`.

After these, it should be possible to remove the `@mut` boxes from `ExtCtxt` altogether, though #11167 is doing some of that so I'm holding off on that for now. This will probably conflict with that PR, so I'm guessing that one will have to be rebased on top of the other.

r? @pcwalton
auto merge of #10885 : kballard/rust/as_mut_slice, r=cmr

This method is primarily intended to allow for converting a [T, ..N] to
a &mut [T].
auto merge of #11169 : alexcrichton/rust/snapshots, r=sanxiyn

Hurray trait coercion!
auto merge of #11182 : luisbg/rust/crateid, r=cmr

Issue #11048
auto merge of #11185 : huonw/rust/doc-ignore, r=cmr

Currently any line starting with `#` is filtered from the output,
including line like `#[deriving]`; this patch makes it so lines are only
filtered when followed by a space similar to the current behaviour of
the tutorial/manual tester.
auto merge of #11190 : eliovir/rust/patch-3, r=alexcrichton

#[ author = "Jane Doe" ]; raises "warning: unknown crate attribute"
replace `pkgid` by `crate_id`
add `comment`
Parse macro_crate!