Fix another missing header file for mcore libgloss

I guess I must have missed this when working through the trivial port specific
changes.

This adds an include of stdlib.h to get a prototype for exit().

Pushed to the trunk.

libgloss/mcore/sbrk.c

@@ -14,6 +14,7 @@
  */
 #include <sys/types.h>
 #include <sys/stat.h>
+#include <stdlib.h>
 #include "glue.h"
 
 extern int _write (int, char *, int);