Holistic refactoring.

Remove "." in coverage output for lines with comments.
Silence complaints in coverage output about unexecuted docstrings.

Eliminate use of inspect module in favor of direct access to frame and
code objects.  We're in a trace function here:  Efficiency counts!

Remove unused code.  Reflow long lines.

Remove backwards compatibility for stored trace output from Zooko's
experiment to add calledfuncs to the pickled dict.

Move code to generate per-file coverage stats to a separate routine.

Replace use of parser module with call to compile.