types/Endianness: Provide enumerated type identifying big or little
endian.
build-aux/infra/types: Ask for endianness when building byte arrays from
fixed-sized byte arrays.
build-aux/infra/types: Generate reader for fixed-size byte arrays.
assembly/ia32_x64: Read and keep immediate values as fixed-size byte
arrays, let users decide when to convert them to signed or unsigned
integers.
assembly/ia32_x64/dom/Instruction: LOOPE and LOOPNZ are branching
instructions.