The following actions should be made to rebuild Qt MYSQL plugin.
- cd qt\5.3\Src\qtbase\src\plugins\sqldrivers\mysql
- qmake INCLUDEPATH+='C:\MySQL\MySQLConnectorC6.1\include' LIBS+="C:\MySQL\MySQLConnectorC6.1\lib\libmysql.lib" mysql.pro
- nmake (in dev console)