Bug #1191458: tracing over for loops now produces a line event

Bug #1191458: tracing over for loops now produces a line event
on each iteration.  I'm not positive this is the best way to handle
this.  I'm also not sure that there aren't other cases where
the lnotab is generated incorrectly.  It would be great if people
that use pdb or tracing could test heavily.

Also:
 * Remove dead/duplicated code that wasn't used/necessary
   because we already handled the docstring prior to entering the loop.
 * add some debugging code into the compiler (#if 0'd out).