Fix memory leak in redis_serialize().

redis_serialize() leaks the zend_string within z_copy in the
redis_sock->serializer == REDIS_SERIALIZER_NONE case when z is not an
IS_STRING. Instead, redis_serialize() should take a copy of the string, return
that with the flag telling the caller to free the string when it's done with
it, and destroy z_copy.

Author: LawnGnome

library.c

@@ -2019,9 +2019,10 @@ redis_serialize(RedisSock *redis_sock, zval *z, char **val, size_t *val_len
 
             /* return string */
             convert_to_string(&z_copy);
-            *val = Z_STRVAL_P(&z_copy);
+            *val = estrndup(Z_STRVAL_P(&z_copy), Z_STRLEN_P(&z_copy));
             *val_len = Z_STRLEN_P(&z_copy);
-            return 0;
+            zval_ptr_dtor(&z_copy);
+            return 1;
 
         case REDIS_SERIALIZER_PHP: