Add @Spell clusters to Vim syntax file

Add @Spell clusters to Vim syntax highlighting file to do spell checking
only inside comments and strings
added empty() to Peekable
extra::ebml: Make reader::Res public

Since reader::vuint_at() returns a result of type reader::Res it makes sense
to make it public.

Due to rust's current behavior of externally referenced private structures,
https://github.com/mozilla/rust/issues/10573, you could still use the result and
assign it to a variable if you let the compiler do the type assignment,
but you could not explicitly annotate a variable to hold a reader::Res.
extra::ebml: Add unit test for vuint_at()
ebml::extra: Optimize reader::vuint_at()

Use a lookup table, SHIFT_MASK_TABLE, that for every possible four
bit prefix holds the number of times the value should be right shifted and what
the right shifted value should be masked with. This way we can get rid of the
branches which in my testing gives approximately a 2x speedup.
renamed empty() to is_empty()
Flag failure functions as inline(never)

The failure functions are generic, meaning they're candidates for getting
inlined across crates. This has been happening, leading to monstrosities like
that found in #11549. I have verified that the codegen is *much* better now that
we're not inlining the failure path (the slow path).
register snapshots
remove the concept of managed-unique from libstd

Closes #11545
Revert "show options for -W help and -W". Fixes #11458.

This reverts commit 1009c21ad7b1db366a5c600946652cc490598ec1.
Use the least significant beat to determine if int/uint is even
libsyntax: Remove the obsolete ability to parse from substrings.

This was used by the quasiquoter.
Allow more "error" values in try_recv()

This should allow callers to know whether the channel was empty or disconnected
without having to block.

Closes #11087
fixup! ebml::extra: Optimize reader::vuint_at()
auto merge of #11112 : alexcrichton/rust/issue-11087, r=brson

This should allow callers to know whether the channel was empty or disconnected
without having to block.

Closes #11087
path: Fix joining Windows path when the receiver is "C:"

WindowsPath::new("C:").join("a") produces r"C:\a". This is incorrect.
It should produce "C:a".
auto merge of #11550 : alexcrichton/rust/noinline, r=thestinger

The failure functions are generic, meaning they're candidates for getting
inlined across crates. This has been happening, leading to monstrosities like
that found in #11549. I have verified that the codegen is *much* better now that
we're not inlining the failure path (the slow path).
Issue #3511 - Rationalize temporary lifetimes.

Major changes:

- Define temporary scopes in a syntax-based way that basically defaults
  to the innermost statement or conditional block, except for in
  a `let` initializer, where we default to the innermost block. Rules
  are documented in the code, but not in the manual (yet).
  See new test run-pass/cleanup-value-scopes.rs for examples.
- Refactors Datum to better define cleanup roles.
- Refactor cleanup scopes to not be tied to basic blocks, permitting
  us to have a very large number of scopes (one per AST node).
- Introduce nascent documentation in trans/doc.rs covering datums and
  cleanup in a more comprehensive way.
auto merge of #11568 : FlaPer87/rust/even, r=alexcrichton

This implementation should be a bit more optimal than calling `self.is_multiple_of(&2)`
Use as_slice() method on option