-- added pickling support (only works if sre is imported)

-- fixed wordsize problems in engine
   (instead of casting literals down to the character size,
   cast characters up to the literal size (same as the code
   word size).  this prevents false hits when you're matching
   a unicode pattern against an 8-bit string. (unfortunately,
   this broke another test, but I think the test should be
   changed in this case; more on that on python-dev)

-- added sre.purge function
   (unofficial, clears the cache)