lua -- remove direct rb-> libc calls infavor of macro substitution WIP

there are no functional changes in this patch
it just makes it easier to build lua in core app
or plugin form

-Update moved some things around messing up compilation on Native targets
due to *errno

Change-Id: I0921df62d72a87516ad95c68e986b5931c35345e

apps/plugins/lua/loadlib.c

@@ -34,9 +34,9 @@
 
 
 static int readable (const char *filename) {
-  int f = rb->open(filename, O_RDONLY);  /* try to open file */
+  int f = open(filename, O_RDONLY);  /* try to open file */
   if (f < 0) return 0;  /* open failed */
-  rb->close(f);
+  close(f);
   return 1;
 }