posix: Consolidate Linux pause syscall

This patch consolidates the pause Linux implementation on
sysdeps/unix/sysv/linux/pause.c.  If defined the pause syscall
(__NR_pause) will be used, other ppoll with 0 arguments will be
used instead.

It has the small advantage of generic pause implementation with
uses rt_sigprocmask plus rt_sigsuspend because it requires only
one syscall and the pause is done atomically regarding signal
handling (for instance, pause may not be interrupted if the
signal arrives between the rt_sigprocmask and rt_sigsuspend
syscall).

Checked on i686-linux-gnu, x86_64-linux-gnu, x86_64-linux-gnux32,
arch64-linux-gnu, arm-linux-gnueabihf, powerpc64le-linux-gnu,
sparc64-linux-gnu, and sparcv9-linux-gnu.

	* sysdeps/unix/sysv/linux/generic/pause.c: Remove file.
	* sysdeps/unix/sysv/linux/sparc/sparc64/pause.c: Likewise.
	* sysdeps/unix/sysv/linux/sparc/kernel-features.h [__arch64__]
	(__NR_pause): Undefine.
	* sysdeps/unix/sysv/linux/pause.c: New file.
	* sysdeps/unix/sysv/linux/syscalls.list: Remove pause from
	auto-generation list.

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

@@ -32,6 +32,10 @@
 # undef __ASSUME_ACCEPT_SYSCALL
 # undef __ASSUME_CONNECT_SYSCALL
 # undef __ASSUME_RECVFROM_SYSCALL
+#else
+/* sparc64 defines __NR_pause,  however it is not supported (ENOSYS).
+   Undefine so pause.c can use a correct alternative.  */
+# undef __NR_pause
 #endif
 
 /* sparc only supports ipc syscall.  */

sysdeps/unix/sysv/linux/sparc/sparc64/Makefile

@@ -9,6 +9,5 @@ sysdep_routines += __start_context
 endif
 
 ifeq ($(subdir),nptl)
-CFLAGS-pause.c += -fexceptions
 CFLAGS-sigsuspend.c += -fexceptions
 endif

sysdeps/unix/sysv/linux/sparc/sparc64/pause.c

@@ -1,9 +0,0 @@
-#include <errno.h>
-#include <signal.h>
-#include <unistd.h>
-#include <sysdep-cancel.h>
-
-#define __sigprocmask(how, set, oset) \
-  INLINE_SYSCALL (rt_sigprocmask, 4, how, set, oset, _NSIG / 8)
-
-#include <sysdeps/posix/pause.c>