[branche 2.5] language_switch - add flag mn_MN

git-svn-id: http://piwigo.org/svn/branches/2.5@22250 68402e56-0260-453c-a942-63ccdbb3a9ee
[branche 2.5] language_switch - add LT

git-svn-id: http://piwigo.org/svn/branches/2.5@22258 68402e56-0260-453c-a942-63ccdbb3a9ee