Add tests checking "remove overlap" resulting spline counts

Add two new test files that more closedly check the results of applying
"remove overlap" operations to glyphs in font files.

Previous tests of "remove overlap" only probed for displayed `stderr`
messages or more dramatically program crashes.  Those didn't directly
address the question "do we (seem to) get the correct output?"

By checking the resulting counts of generated splines we can more closely
approximate the only really complete test, eyeballing the output font.

`tests/test1008a.py` uses new font file `tests/fonts/OverlapCounts1.sfd`
This font is derived from an SVG font file having many overlaps and
coincident rounded corners and terminals, and that demonstrated 
problems until recently fixed.  (Thank you, Frank!)

`tests/test1008b.py` re-uses old font file `tests/fonts/OverlapBugs.sfd`
This font contains many torture-test glyphs from GW.  And some of
these glyphs currently produce quite puzzling results upon "remove
overlap" and should be re-examined to determine whether some of
the results are indeed failures.  Currently this new test does
announce failure on 12 of the total 128 glyphs in the font.


I think I should open an issue summarizing the unexpected results
from checking the old torture-test font.  It would seem that one or 
several of these glyphs are encountering bugs, *or* that perhaps
there needs to be more description of how sensitive "remove overlap"
is to things like spline directions.