MANIFEST - add t/decode_d64.t (new test file)
Decimal64.pm - add decode_d64() and associated subs
Decimal64.xs - add XSubs for decode_d64() to use
Makefile.PL - detect endianness - needed for decode_d64()
Changes - Update
t/decode_d64.t - new file
t/aab_basic.t - check that endianness has been registered