[Pyrex] Pyrex optimization

[Jiba]

> It uses the "PySequence_" methods. On the other hand, the obfuscated 
> _heapq_ uses the "PyList_" methods but that was because the C heapq 
> module which is slated to be added to Python does that too. The Pyrex 
> version is as fragile and backwards incompatible as the C version and 
> almost as fast. If I were not competing with a module that already 
> "cheated" I wouldn't cheat.

OK, i was not really aware of what a sequence was, since Python does not
use the word "sequence" itself in Python (rather at the C level, but
thanks to Pyrex i don't know about this level ;-)

Jiba