Fix warning: label 'done' defined but not used [-Wunused-label]

Author: remicollet

Diff for: g_fmt.c

@@ -94,6 +94,8 @@ char *php_memcached_g_fmt(register char *b, double x) {
 
  done0:
 	zend_freedtoa(s0);
+#ifdef IGNORE_ZERO_SIGN
  done:
+#endif
 	return b0;
 }