Test POSIX 1003.1 2016 chapter 13 "Headers".

And fix one thing that this found: apparently <stdlib.h> should also
make the various *WAIT* macros available.

Bug: N/A
Test: builds
Change-Id: Id879bf3c1bddd1170261a809e7280150a74d6b3d
diff --git a/libc/include/stdlib.h b/libc/include/stdlib.h
index cf0dea8..1ae3c6e 100644
--- a/libc/include/stdlib.h
+++ b/libc/include/stdlib.h
@@ -29,12 +29,12 @@
 #ifndef _STDLIB_H
 #define _STDLIB_H
 
-#include <sys/cdefs.h>
-#include <xlocale.h>
-
 #include <alloca.h>
+#include <bits/wait.h>
 #include <malloc.h>
 #include <stddef.h>
+#include <sys/cdefs.h>
+#include <xlocale.h>
 
 __BEGIN_DECLS