TRANSACTION

Problem
-------

When GTID skipping transactions using mysql client program, when the
transaction contains a binary log dump including "use `<DATABASE>`"
statements, the "use" statement is failing accusing:

USE must be followed by a database name
ERROR 1046 (3D000) at line ...: No database selected

Analysis
--------

When the USE statement has quotes, the mysql client program asks the
server to translate the database name, issuing two statements to the
server:
1. USE `database`
2. SELECT DATABASE();

When GTID skipping a transaction, the USE `database` is taking no
effect, leading to SELECT DATABASE() to return NULL.

Fix
---

Made SQLCOM_CHANGE_DB also an "innocent" statement from the GTID skip
point of view. In this way, the USE `database` will take effect and the
SELECT DATABASE() should not return NULL anymore.