renaming a function for clarity

lib/fimg-core.c

@@ -194,7 +194,7 @@ int		foo;
 fprintf(stderr, ">>> %-25s ( %p %p )\n", __func__, from, to);
 #endif
 
-foo = fimg_images_compatible(from, to);
+foo = fimg_images_not_compatible(from, to);
 if (foo) {
 	fprintf(stderr, "%s: pics not compatible (%d)\n", __func__, foo);
 	return foo;