This patch removes a bunch of superfluous #include directives: if

postgres.h or c.h includes a system header (such as stdio.h or
stdlib.h), there's no need to specifically include it in any of the .c
files in the backend.

Neil Conway

src/backend/port/darwin/system.c

@@ -37,11 +37,8 @@
 static char sccsid[] = "@(#)system.c	8.1 (Berkeley) 6/4/93";
 #endif   /* LIBC_SCCS and not lint */
 
-#include <sys/types.h>
 #include <sys/wait.h>
 #include <signal.h>
-#include <stdlib.h>
-#include <stddef.h>
 #include <unistd.h>
 #include <paths.h>
 #include <errno.h>