Adds a regression test based on klauspost/compress#186. This necessitated some related changes:
* Mark "RET" as a terminal instruction
* printer refactor to maintain compatibility with asmfmt
* Tweaks to other regression tests to ensure they are run correctly in CI
Updates #100#65#8
Adds support for a `CancellingInputs` instruction flag, to indicate cases like `XORQ R10, R10` where the instruction actually does not depend on the value of `R10` at all.
Closes#89
The Go assembler merges MOVD/MOVQ instruction forms. The logic in the
avo instruction loader was discarding the MOVD forms. This diff should
merge them correctly.
Updates #50
