x86_64: new syscall

Add epoll_pwait()

(akpm: stolen from Andi's queue, because I want to send the signalfd patches
which also add syscalls.  Not sure what the __IGNORE_getcpu is for).
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/asm-x86_64/unistd.h

@@ -621,6 +621,9 @@ __SYSCALL(__NR_vmsplice, sys_vmsplice)
 __SYSCALL(__NR_move_pages, sys_move_pages)
 #define __NR_utimensat		280
 __SYSCALL(__NR_utimensat, sys_utimensat)
+#define __IGNORE_getcpu		/* implemented as a vsyscall */
+#define __NR_epoll_pwait	281
+__SYSCALL(__NR_epoll_pwait, sys_epoll_pwait)
 
 #ifndef __NO_STUBS
 #define __ARCH_WANT_OLD_READDIR