Bug 936554: enable home, plugincheck, firefox/new for xh

This locales is not available on the PHP side (/trunk/xh), only on
Bedrock (/trunk/locales/xh). We don't need it on prod at the moment,
only on www-dev.
Merge pull request #1390 from flodolo/enable_xh

Bug 936554: enable home, plugincheck, firefox/new Bedrock redirects for xh