Minor reordering of `#include`s fixing compilation on AIX

This helps ensure that system includes on some more fragile
platforms (like e.g. AIX) see a more consistent set of CPP defines,
and consequently reduce the risk of conflicting typdefs/prototypes
being exposed.

rts/PathUtils.c

-#include <string.h>
-#include <stddef.h>
-
 #include <Rts.h>
 #include "RtsUtils.h"
 #include "PathUtils.h"
 
+#include <string.h>
+#include <stddef.h>
+
 #include <libgen.h>
 #include <ctype.h>
 

rts/linker/LoadArchive.c

-#include <string.h>
-#include <stddef.h>
-
 #include <Rts.h>
 #include "PathUtils.h"
 
@@ -20,6 +17,8 @@
 #  include <mach-o/fat.h>
 #endif
 
+#include <string.h>
+#include <stddef.h>
 #include <ctype.h>
 
 #define FAIL(...) do {\

rts/sm/CNF.c

@@ -11,7 +11,6 @@
 #define _GNU_SOURCE
 
 #include "PosixSource.h"
-#include <string.h>
 #include "Rts.h"
 #include "RtsUtils.h"
 
@@ -25,6 +24,8 @@
 #include "Trace.h"
 #include "sm/ShouldCompact.h"
 
+#include <string.h>
+
 #ifdef HAVE_UNISTD_H
 #include <unistd.h>
 #endif