Implement changes from yesterday morning's meeting (10/21/2011):

Implement changes from yesterday morning's meeting (10/21/2011):

* OutputChannel::lemma() now returns an unsigned int.  This facility isn't functional yet, but the signature is there.  For now, it always returns the current user level (which is "correct" from the interface point of view, but not what we want).
* Pseudobooleans disabled.  This should fix some quantifier benchmarks Andy's been working with on the quantifiers2 branch.
* --limit / --time-limit options renamed --rlimit and --tlimit.

There may be slowdown from disabling pseudobooleans.