Bump CI Go versions to 1.16 and 1.17. Update build tags with `go:build` equivalents. Upgrade asmfmt tool for new `go:build` support. Updates #183
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