Fix GTK2 compatibility

Fix two GTK2 version issues: VNC segfaults and RDP plugin memory leak.
Merge pull request #293 from amon-sha/fix_gtk2_compatibility

Fix GTK2 compatibility
Update .po files and merge them with Ubuntu's one

Updates .po files and merged with http://packages.ubuntu.com/trusty/translations/
Merge branch 'nlocals' of https://github.com/giox069/Remmina into gtk3