[JWasm move] Specify struct names where necessary

It may look redundant and it surely bloats the code, but well, registers don't
have types, so it really *is* good coding style to do this everywhere.
[JWasm move] Fix the interrupt vector declarations in c0[data].asm

The leniency! It hurts!
[JWasm move] Prefixes must be on the same line as the modified instruction
[JWasm move] Avoid "push large"

For 32-bit immediate values, PUSH by itself is enough. For everything else,
PUSHD works in both TASM and JWasm.

Also, could it be...? Could we actually move to JWasm without breaking the
build in TASM at all?