Make modcss.inc work with allow_url_fopen = Off

Alternatively use the PHP cURL extension
modcss.inc: Fixed CS
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