ANSIfication step 2: make sure all needed prototypes are available, and all needed
header files included.
diff --git a/Mac/mwerks/malloc/malloc.c b/Mac/mwerks/malloc/malloc.c
index 7d0fb6c..38bd32a 100644
--- a/Mac/mwerks/malloc/malloc.c
+++ b/Mac/mwerks/malloc/malloc.c
@@ -78,7 +78,9 @@
 #include <stdlib.h>
 #include <string.h>
 
+#ifndef NULL
 #define	NULL 0
+#endif
 
 static void morecore();