Add support for mac.l, clrmac, and addv/subv

[attilavs2]

[lephe]

addv/subv are incorerct, you should check for signed overflow. Overflow occurs if you add two numbers with the same sign and the result's sign is not the same as the operands'. The logic is the same for subv but flipping the sign of the second operand. You can check the SH4 manual for a pseudo-code version of these.

With the current code, addv reports overflow for -1+0, -1+-1, -1+1...

Also you must set T inconditionally.

[attilavs2]

True, i didn't think enough about it. Will try to find time to fix it tonight.

[attilavs2]

Basing myself on the manual, i should have corrected the implementations

[attilavs2]

I removed movco/movli at Circuit10's request (on discord)