Update to 4.5.3

* Change to 4.5 branch

Changelog:
Version 4.5.3 Nov 27th 2012
    Fix the new from url button
    Fix a memory overflow with downloading of big files via WebDAV
    Better error output in case of DB problems
    Fix problems with uploading files who have special characters in the name
    Improved reverse proxy and load balancer support
    Fix wrong folder size calculation
    Improved share link generation
    Fix the syncing of the Shared folder
    Fix Sharing by link from within Shared folder
    Several LDAP integration fixes
    Fix support for PostgreSQL
    Several WebDAV fixes
    Fix drag and drop uploading
    Improved translations
    Several Gallery fixes
    Several Contacts fixes
    Smaller fixes

Version 4.5.2 Nov 14th 2012
    Fix syncing of shared folder
    Various sharing bugs fixed
    Fix bug with deleting users
    Fix check if resharing is allowed
    Fix webdavauth app
    Several ldap fixes
    Fix data migration
    Fix folder uploads
    Fix generatino of etags
    Fix user specific mount configuration
    Several PostgreSQL fixes
    Improved performance of file updates
    Fix some php warnings
    Fix filesize calculation
    Add visual feedback if password is set
    Various smaller fixes
    Several critical security fixes
    XSS vulnerability in user_webdavauth (oC-SA-2012-003)
    Code Execution in /lib/migrate.php (oC-SA-2012-004)
    Code Execution in /lib/filesystem.php (oC-SA-2012-005)

(ryoon)