allow underscore in ALIAS name (Fixes: #3866)

Florian Schaal

2016-04-30 8beb039f0b7d23b03f7963c3a56c8dde65af3b6b

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ALTER TABLE  `sys_session` CHANGE  `session_id`  `session_id` VARCHAR( 64 ) CHARACTER SET latin1 COLLATE latin1_swedish_ci NOT NULL;