Rollup of 7 pull requests#42010

Closed

frewsxcv wants to merge 19 commits intorust-lang:masterfrom

frewsxcv:rollup

Commits on May 9, 2017

Prohibit parenthesized params in more types.
qnighy
committed

Commits on May 14, 2017

Explain why `thread::yield_now` could be used.
Felix Raimundo
committed
Improve `thread::Builder` documentation.
Felix Raimundo
committed
Remove rustc_llvm dependency from rustc_metadata
Robin Kruppe
committed
rustdoc: Display `extern "C" fn` instead of `extern fn`
ollie27
committed

Commits on May 15, 2017