Make modcss.inc work with allow_url_fopen = Off

Alternatively use the PHP cURL extension
modcss.inc: Fixed CS
Don't hide upload dialog if no file was selected. Display an alert message for all empty file uploads (#1489685)
Map fr => fr_FR for transifex pulling
Synchrnonized translations from Transifex
Disable link registering mailto: protocol handler if not supported by the browser (#1489569)
Drop support for PHP < 5.3.7
Merge branch 'master' of github.com:roundcube/roundcubemail
Merge pull request #167 from Steffen185/allow_url_fopen_off

Make modcss.inc work with allow_url_fopen = Off
CS fixes
Make sure parent folder selector always contains parent folder
of current folder, even if it does not exist
Skip IMAP SORT request if folder is empty
Fix fatal error in database_attachments plugin under some conditions (#1489726)