Don't use wildcard cache clearing for language based cache keys

Wildcard cache clearing isn't supported by a number of caching backends, particularly memcache. That means when they receive a wildcard, they have to wipe the entire cache bin or risk stale data. Not good at all. With languages, we know what's on the system, so we can figure out what the keys are, and clear one at a time instead.

I didn't check for other places where this happens, but I'm sure there's others.