Remove __ASSUME_EVENTFD2, move eventfd to syscalls.list.

Given current Linux kernel version requirements, we can assume the
presence of the eventfd2 syscall.  This means that __ASSUME_EVENTFD2
can be removed, and a syscalls.list entry suffices for eventfd instead
of needing a .c file.  This patch implements those changes.

Tested for x86_64 and x86 (not that that means much, given the lack of
testsuite coverage for eventfd).

	* sysdeps/unix/sysv/linux/kernel-features.h (__ASSUME_EVENTFD2):
	Remove macro.
	* sysdeps/unix/sysv/linux/eventfd.c: Remove file.
	* sysdeps/unix/sysv/linux/syscalls.list (eventfd): New syscall
	entry.

ChangeLog

@@ -1,5 +1,11 @@
 2016-03-17  Joseph Myers  <joseph@codesourcery.com>
 
+	* sysdeps/unix/sysv/linux/kernel-features.h (__ASSUME_EVENTFD2):
+	Remove macro.
+	* sysdeps/unix/sysv/linux/eventfd.c: Remove file.
+	* sysdeps/unix/sysv/linux/syscalls.list (eventfd): New syscall
+	entry.
+
 	* sysdeps/unix/sysv/linux/kernel-features.h (__ASSUME_FALLOCATE):
 	Remove macro.
 	* sysdeps/unix/sysv/linux/wordsize-64/posix_fallocate.c: Do not

sysdeps/unix/sysv/linux/kernel-features.h

@@ -83,7 +83,6 @@
    2.6.27.  */
 #define __ASSUME_IN_NONBLOCK	1
 #define __ASSUME_PIPE2		1
-#define __ASSUME_EVENTFD2	1
 #define __ASSUME_SIGNALFD4	1
 #define __ASSUME_DUP3		1
 

sysdeps/unix/sysv/linux/syscalls.list

@@ -13,6 +13,7 @@ epoll_create	EXTRA	epoll_create	i:i	epoll_create
 epoll_create1	EXTRA	epoll_create1	i:i	epoll_create1
 epoll_ctl	EXTRA	epoll_ctl	i:iiip	epoll_ctl
 epoll_wait	EXTRA	epoll_wait	Ci:ipii	epoll_wait
+eventfd		EXTRA	eventfd2	i:ii	eventfd
 execve		-	execve		i:spp	__execve	execve
 fdatasync	-	fdatasync	Ci:i	fdatasync
 flock		-	flock		i:ii	__flock		flock