Fix the cycles (a clear method, called after render, that removes

Fix the cycles (a clear method, called after render, that removes
the bound methods from the globals dict).
Use cl.filter instead of cl.list followed by sortfunc. For some
backends (Metakit), filter can sort at C speeds, cutting >10 secs
off of filling in the <select...> box for assigned_to when you
have 600+ users.

git-svn-id: http://svn.roundup-tracker.org/svnroot/roundup/trunk@822 57a73879-2fb5-44c3-a270-3262357dd7e2