Improved dovecot version detection in installer for Fedora and CentOS.

Till Brehm

2014-10-19 b79f6ca284856d5ad1e260540b418b7eb634bc16

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