Added some more unimplemented functions

src/backing.c

@@ -63,4 +63,9 @@ bool backing_exists(const char* backing) {
 		return false;
 
 	return true;
-}
+}
+
+uint64_t get_backing_creation_time(const char* backing) {
+	// A valid backing name is a number, corresponding to the timestamp of the backing disk creation
+	return strtoull(backing, NULL, 10);
+}