added cPickle_PyMapping_HasKey to replace leaking PyMapping_HasKey
lists and dictionaries are put in memo before saving their items
put2() added so that refcnt check isn't done in various cases

into object initializer, so it gets applied in all cases.

added check for empty tuples before memo check in save_tuple()

functions so that internal calls could be made without having to
go through PyArg_ParseTuple

fixed bug in load_short_binstring()