vim: Fix :RustRun when cwd has a space in it
regex: Fix control flow in the parser
regex: Escaped literals can end ranges
regex: The first range in a character class can start with a left bracket
Guide: Patterns: use non-x variables in match blocks
Guide: Closures: minor wording fixes
Guide: Closures fix suggested by @cakebaker
Guide: Iterators, Macros and Unsafe wording fixes
simplify shootout-reverse-complement.rs

Simpler, safer and shorter, in the same spirit of the current version, and the
same performances.
libcore: Inline atomic constructors.

Servo really wants this.
Fix some wording about errors

see https://github.com/rust-lang/rust/pull/18176#discussion_r19374679
return &mut T from the arenas, not &T

The arenas write the value to memory and then return a non-aliasing
reference to it. The returned reference can be mutable and can be
coerced to an immutable one.

[breaking-change]
Small grammar fix in rustdoc.md

Happened to be reading through
Use PascalCase for token variants
Convert some token  functions into methods
Use an enum rather than a bool in token::Ident
Move token-to-string functions into print::pprust
Respect mut in &mut str in astconv

Closes #17361
Add regression test for issue #17361
Remove double negation from sqrt's doc comment