Add 16-bit ASR immediate instruction
Make shift immediates decimal, since they are always >= 32
Provide bool conversion functions

Rename booltoi to booltou, since it returns a uint8, and provide a
utobool.
Add 16-bit ADD (register) T1 encoding
Provide method to determine whether to update flags

Determined based on SetFlags setting and current register state.
Provide Shift type

This type simply wraps a shifting function and amount, providing a
simple way to pass the information around, and evaluate it.
Add 16-bit ADD (sp plus register) T1 encoding
Add ADD (sp plus register) encoding T2