Silence some Valgrind errors

Need to have the allocated memory explicitly cleared for Valgrind
to know it.  We should probably start using calloc or something...

src/region.c

@@ -91,6 +91,7 @@ int nrect;
     NhRegion *reg;
 
     reg = (NhRegion *) alloc(sizeof(NhRegion));
+    (void) memset((genericptr_t)reg, 0, sizeof(NhRegion));
     /* Determines bounding box */
     if (nrect > 0) {
         reg->bounding_box = rects[0];