8.2.1 - x64 register phrase parsing

Fix x64 phrase register parsing.

IDA-6.x

With IDA 7.4 dropping backwards-compatibility for IDA 6.x, so will Sark.
Bugfixes will still be added to the IDA-6.x branch, but it will no longer be under active development. (Yes, I know development has not been active at all for a few years now...)