Makes the peepholer output more compact, more readable,
and a bit faster.  Also saves a bit of space in pyc files.

* Uses NOPs instead of JMP+3 or JMP+2.
* Then, makes a pass to eliminate the NOPs (which
entails re-aligning the jump targets and linenotab).
* Add a transform to get rid of the unnecessary Return
Nones followed by another Return in the same block.
* Fixed the overflow test (codelen < 65000) to coerce
codelen to unsigned before the check.

Michael, I would appreciate it if you could give this a
second look just to make sure before I check it in.  I
would like it to go in well before the next alpha.  The
patch passes the test suite, runs all my own apps, and
has run on my machine for about a week with any issues.
If you don't have time to give it a once over, please
assign to Armin.

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Added a revision with better formatting and more tests.

This patch is open for whoever has time to look at it first.

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No reviewers responded to my emails.  Applying now so that
it gets exercised as much as possible before the next alpha
release.

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Raymond, for the future: it's pretty rare for me to read my
email at the weekend...