This is a cherry-pick of commit d010030ad5 from the master branch.
Conflicts:
Makefile.am
include/uv.h
include/uv/unix.h
libuv.nsi (deleted)
src/unix/pthread-barrier.c (deleted)
PR-URL: https://github.com/libuv/libuv/pull/1850
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
