These instructions have a fixed register constraint; the shift amount is
passed in CL.
Add meta language syntax so a fixed register can be specified as
"GPR.rcx".
Tabulate the Intel opcode representations and implement an OP() function
which computes the encoding bits.
Implement the single-byte opcode with a reg-reg ModR/M byte.
The intel, arm32, and arm32 targets were only defined in the meta
language previously. Add Rust implementations too.
This is mostly boilerplate, except for the unit tests in the
registers.rs files.
Add a RegBank class for describing CPU register banks.
Define register banks for all the ISA stubs. The ARM32 floating point
bank in particular requires attention.
The Intel ISA handles both 32-bit and 64-bit code.
ARM is split into separate arm32 and arm64 ISAs since the architectures
have little in common in instruction encodings and register files.
