epoll keyed wakeups: make sockets use keyed wakeups

epoll keyed wakeups: make sockets use keyed wakeups

Add support for event-aware wakeups to the sockets code.  Events are
delivered to the wakeup target, so that epoll can avoid spurious wakeups
for non-interesting events.

Signed-off-by: Davide Libenzi <[email protected]>
Acked-by: Alan Cox <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: David Miller <[email protected]>
Cc: William Lee Irwin III <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>