fixed build with changed install directories (defaults/pref -> defaults/preferences)
enabled GStreamer support on 12.1 and newer
made toolkit packaging errors non-fatal (as they are expected with system NSPR and NSS anyway)
<?xml version="1.0" encoding="UTF-8"?>
<mime-info xmlns="http://www.freedesktop.org/standards/shared-mime-info">
<mime-type type="application/x-xpinstall">
<comment xml:lang="en">Mozilla Cross-Platform Installer Module</comment>
<glob pattern="*.xpi" />
</mime-type>
</mime-info>