fix constant folding of PrimaryCmpNode operands
optimise object.append() only when return value is not used and adapt signature accordingly
disable exception check for special C return type (always assume that it's an exception when -1 is returned)

--HG--
extra : amend_source : 88f30462a27faf52fcee83af0d1dce714e4f7e69
inline bytearray.append()
add integer fast-path to __Pyx_PyIndex_AsSsize_t()