Enable HPy on win64
Now that cpyext is functional, _hpy_universal (almost) translates properly and can be enabled. The only change needed is to add a range check in HPyLong_AsLong and related functions, copied from the cpyext functions.
I did not run any tests since they don't work on win32 either (the extra_tests step on the win32/win64 buildbots crashes before it gets to hpy with
INTERNALERROR> UnicodeEncodeError: 'charmap' codec can't encode character '\u03be' in position 120: character maps to <undefined>, running locally I get the error
cl : Command line error D8021 : invalid numeric argument '/Wfatal-errors').