Decimal64.pm - align with Math::Decima128
Decimal64.xs - align with Math::Decima128
MANIFEST - add new test files
t/PVtoD64.t - new test file
t/MEtoPV.t - new test file
t/Inf_Nan.t - new test file
t/DPDtoD64.t - new test file
t/decode_cross_checks.t - new test
t/assignDPD.t - new test file
t/assignPV.t - new test file
t/Exp10.t - new test file