Added basic framework for backend.
Add simple RTS and get basic codegen working.
Increase the allocation size to 64K to reduce syscalls
Remove commented-out debug code
Add normal and composed blocks
Make compare-simplifed allow commands
Add quote operator and simple ABC parser
Skip keep and affine operators -- no runtime behaviour
Add num and digit operators
Switch to doubles, use union for type-punning
Fix incorrect implementation of drop.
Add inverse, negate, and divmod
Fix malloc to work for non-uniform allocation sizes
Use full initial environment (no powerblock)
Correct order of return values in divmod
Ignore whitespace
Don't hardcode input into backend
Make test.sh exit when something fails
Add remaining opcodes
Fix test.sh not failing on parse error