[krbdev.mit.edu #1237] Merge the profile library with meeroh optimizations

[Ken Raeburn via RT]

Yes, the locking model needs fixing.

profile_update_file_data can free and then create data->root, but
data->root isn't protected by the mutex, so another thread using a
different prf_file_t handle may be reading it while it's being freed.

I suspect the right fix is going to involve changing the keying of the
linked list to be by timestamp as well as by name.  Need to think
through how that's going to affect the update_file part.

For now, what's there should work just fine as long as the config file
isn't modified while a process is using it in multiple threads.