[Bug#1071587] Dont serve php as plaintext, if we turn off php engine

This applies to all currently available versions (goes back to initial commit of php.conf), should be merged to all versions up to current.

The php.conf distributed disables the php engine for userdirs, but does not block php files from being served from them. This causes a default install to serve the php source as plaintext. Since many common php webapps still keep passwords in *.inc.php config files inside web accessible dirs, this allows those passwords and other config data to be accessed by anyone requesting the proper url. This commit adds a directive inside the existing directive to prevent serving .ph?? files as plaintext when the php engine is disabled here.