mpatch: Fix for malloc corner case on AIX

mercurial/mpatch.c

@@ -62,6 +62,9 b' static struct flist *lalloc(int size)'
 {
 	struct flist *a = NULL;
 
+	if (size < 1)
+		size = 1;
+
 	a = (struct flist *)malloc(sizeof(struct flist));
 	if (a) {
 		a->base = (struct frag *)malloc(sizeof(struct frag) * size);