linux: try epoll_pwait if epoll_wait is missing

It seems that epoll_wait is implemented in glibc in terms of epoll_pwait and
new architectures (like arm64) do not implement the epoll_wait syscall at all.
So if epoll_wait errors with ENOSYS, just call epoll_pwait.

This is a backport of 861de3d71d40bdd22712f0079cd38f41be75010d for v0.10
branch.
windows: map ERROR_INVALID_DRIVE to UV_ENOENT

Backport c44f264641bd60bdc53b6e3f2e56d82ba43011d8 for v0.10 branch.
2014.10.21, Version 0.10.29 (Stable)

Changes since version 0.10.28:

* darwin: allocate enough space for select() hack (Fedor Indutny)

* linux: try epoll_pwait if epoll_wait is missing (Michael Hudson-Doyle)

* windows: map ERROR_INVALID_DRIVE to UV_ENOENT (Saúl Ibarra Corretgé)
Now working on v0.10.30