alpha: Wire up missing/new syscalls

This wire up the: fallocate, timerfd_create, timerfd_settime,
timerfd_gettime, signalfd4, eventfd2, epoll_create1, dup3, pipe2,
inotify_init1, preadv, pwritev and rt_tgsigqueueinfo syscalls for
the alpha port.

For umount2, alpha have an "old" and "new" version called: oldumount and
umount; so ignore umount2.

Rebased on top of 6e17e8b9 by Matt
Turner.

Signed-off-by: Daniele Calore <orkaan@orkaan.org>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Signed-off-by: Matt Turner <mattst88@gmail.com>