Xext: Warning fix for shm.c

shm.c: In function 'CheckForShmSyscall':
shm.c:182:5: warning: function declaration isn't a prototype [-Wstrict-prototypes]

Signed-off-by: Jon TURNEY <jon.turney@dronecode.org.uk>
Reviewed-by: Alan Coopersmith <alan.coopersmith@oracle.com>
Reviewed-by: Colin Harrison <colin.harrison@virgin.net>

Xext/shm.c

@@ -179,7 +179,7 @@ SigSysHandler(int signo)
 
 static Bool CheckForShmSyscall(void)
 {
-    void (*oldHandler)();
+    void (*oldHandler)(int);
     int shmid = -1;
 
     /* If no SHM support in the kernel, the bad syscall will generate SIGSYS */