Couldn't apply cleanly the patch, as it appears to be a diff in other
format.

Anyway, applied it by hand, and now I attach the correct svn diff.

The test cases run ok with this change, and the problem is solved.

Regarding the delay introduced, I tested it with:

  $ ./python timeit.py -s "import re;r=re.compile('a?a?a?a?a?aaaaa')"
"r.match('aaaaa')"

Trunk:
  100000 loops, best of 3: 5.4 usec per loop
  100000 loops, best of 3: 5.32 usec per loop
  100000 loops, best of 3: 5.41 usec per loop

Patch applied:
  100000 loops, best of 3: 7.28 usec per loop
  100000 loops, best of 3: 6.79 usec per loop
  100000 loops, best of 3: 7.00 usec per loop

I don't like that. Anyway, I do NOT trust for timing the system where
I'm making the timing, so you may get different results.

Suggestions?