keep both versions of china/taiwan localization icons (bug 1041520)

This fixes the immediate problem, but does highlight that we localize china and taiwan to cn / tw in some places and zh-cn / zh-tw in other places. I don't know how big a deal that is.
`tw` isn't in the [locales list in `l10n.js`](https://github.com/mozilla/fireplace/blob/master/src/media/js/l10n.js#L9)?