Rationalised use of #includes to be more standards-compliant.

lang/occam/comp/report.c

@@ -3,6 +3,8 @@
  * (c) copyright 1987 by the Vrije Universiteit, Amsterdam, The Netherlands.
  * See the copyright notice in the ACK home directory, in the file "Copyright".
  */
+
+#include <stdlib.h>
 #include <system.h>
 
 extern int err, lineno;