forum_access_access() returns false information

While writing some code that was using forum_access.module for a few things, I encountered a bug in forum_access_access(). The static caching was only caching the result corresponding to the $tid passed in, and not caching results for different $type or $account values.

This could (and did in my case) result in incorrect information being returned by forum_access_access() on subsequent calls.

To fix this, I've patched against forum_access.module 5.x-1.9 to cache the other pertinent argument values along with the result they yield. Patch is attached.