rt: Fix child-iteration bug in crate map.
std: add #[cfg(test)] reference to extra so we can benchmark libstd.
std: add preliminary str benchmark.
std: add #[bench] benchmarks for global and local heaps.
std: add #[bench] benchmarks for rand.
std: add #[bench] benchmarks for num::strconv
std: add benchmark for allocating-and-dropping a struct with a dtor.
std: various additional language benchmarks in util.
Add a test for #5844 (a closed issue now)
test/run-fail: Un-xfail a test, make some other xfailed ones compile (they still don't work).
Added missing memory orderings for atomic types.
Remove unused variables in `compile_submatch`.

Just an minor cleanup.

Signed-off-by: OGINO Masanori <masanori.ogino@gmail.com>
rustc: remove some dead functions
tidy: allow arbitrary spaces between // and NOTE

`make tidy` now detects `//NOTE`, `//  NOTE`, etc.
This also removes the extra empty line emitted after each warning.

Fixes #6060
std: wrap "long" utf8 lines.
std: rename str.as_bytes_with_null_consume to str.to_bytes_with_null
std: remove os::as_c_charp
std: move str::as_buf into StrSlice
std: move StrUtil::as_c_str into StrSlice
std: add test for str::as_c_str