Add hook "message_check_safe"

This hook can be used by https://github.com/JohnDoh/Roundcube-Plugin-Global-Address-Book to mark messages as safe whose sender exists in the global address book
Support Alias-to-User lookup with virtuser_query
Update newmail_notifier to use W3C Notification

Update newmail_notifier plugin to use W3C Notification object if
possible.  Include fix for Chrome/Chromium.
Don't set the dn variable unless it's needed.
Add more icons sizes to favicon.ico's
Extend basic notification to add a star icon overlay if we're in IE Pinned site mode (Win7+).
The star icon is taken from Xiao Icon set (http://delacro.deviantart.com/art/Xiao-Icon-84772282).
Update rcube_install.php

write config file automatically to RCUBE_CONFIG_DIR
Update config.php

write config file automatically to RCUBE_CONFIG_DIR
Respect HTTP_X_FORWARDED_FOR and HTTP_X_REAL_IP variables for session IP check
Updated changelog
Added Luxembourgish localizations
Merge branch 'patch-1' of https://github.com/gerundt/roundcubemail into gerundt-patch-1
from pull request #74
Merge pull request #87 from rimas-kudelis/master

Merge pull request #87 from rimas-kudelis: additions to newmail_notifier
Merge pull request #64 from Steffen185/patch-2

Add hook "message_check_safe"
Update config.php

-Replace tabs with spaces.
-Replace the word "files" with "files", because there is only one
Keep unknown/plugin config options; only skip officially obsoleted ones
Merge pull request #90 from Dennis1993/master

Write config file automatically to RCUBE_CONFIG_DIR (if writeable)
Fix codestyle and indentation; use new save function in update script