simplify constant folded comparison code a little and extend the test for it
remove redundant code
undo the Python-optimisationism of assigning bound/unbound methods to local variables when Cython can call a builtin C function instead

--HG--
extra : amend_source : 121eadd540f25f9e43f6e6b60853eeab18d11620
fix constant folding with false partial result