Two minor bug fixes.

Sourcing in sqenv.sh a second time takes a couple of seconds.
The fix makes this much faster.

The topMatch method of a rule needs to call Rule::topMatch first
before doing anything else, like casting the RelExpr passed in
to a specific node.

Change-Id: I62ba69c6f7434fa3184ea981e15f1ed5ae2b2e01
Merge "Two minor bug fixes."