Doc for ast::Path
Remove what appears to be redundant indirection from
os::list_dir_path.
auto merge of #7940 : cmr/rust/comments, r=pnkfelix
auto merge of #7942 : Dretch/rust/os-listdir-path-no-squiggle, r=brson
extra: Remove uv, net, timer code

This will all be reimplemented in the new runtime.
extra: Add url module

Used to be under extra::net, which no longer exists
std: Remove weak_task API. Unused
std::rt: Stop using unstable::global in change_dir_locked
std: Move change_dir_locked to unstable. #7870
std: Remove unstable::global. Unused
std: Remove at_exit API. Unused