add: galloc: leak check

src/galloc.🗿

@@ -157,3 +157,8 @@ free(ptr)
 		last_block = next_block;
 	galloc_merge_blocks(first_block, last_block);
 }
+
+leaks()
+{
+	return (heap + LOCATION_NEXT != NULL);
+}

tests/galloc.🗿

@@ -16,4 +16,7 @@ main()
 
 	ptr2 = galloc(0x9000);
 	test_num(ptr2, 0, "alloc too big");
+	free(ptr2);
+
+	test_num(leaks(), 1, "leaks");
 }