pyLocation_Hash returns spurious exception value

[Hoikas]

pyLocation_Hash can return -1, Python's magical "hey there was an exception" value in cases when there is no error (there should never be an error for hashing locations). This value (and the exception) has been observed on default-inited plLocation objects.

[branan]

It looks like it will also throw an exception when attempting to hash a location with a universal version set, since unparse is not defined for that.

We should probably just implement proper hashing of plLocation (prefix,page) instead of relying on unparse