Clean up, formatting, comments. No functional change.
Add an assert that we have a scope that matters for methods
and remove a call to getNonCompileUnitScope as a method
shouldn't be in the compile unit scope.
Make sure we're not attempting to construct a subprogram DIE
twice and just look up the value. Fix the one case where
we were trying to create a subprogram DIE and we should already
have had one. Reflow formatting in collectDeadVariables while fixing.