Implement inline asm constraints

[redstar]

The following constraint are supported by gcc:

• [ ] I requires a non-negative 16-bit value.
• [ ] J requires a non-positive 16-bit value.
• [ ] K requires a non-negative value < 32.
• [ ] L requires a constant with only the upper 16-bits set.
• [ ] M requires constant values that can be formed with `set'.
• [ ] N requires a negative value.
• [ ] O requires zero.
• [ ] P requires a non-negative value