Add a way to disable replaced instruction warnings

[sikthehedgehog]

I tried building the SLZ decompressor as a test (https://github.com/sikthehedgehog/mdtools/blob/master/slz/md/slz.68k) and got these warnings:

Warning: AND should be ANDI.
On line 40 of 'slz.68k'...
    and.w   #$0F, d4

Warning: EOR should be EORI.
On line 52 of 'slz.68k'...
    eor.w   #$0F<<2, d4

There's probably a lot of old code written on the assumption that the assembler will pick the correct variant (like the above two, or move vs. movea, or writing movep with (an) instead of 0(an)). It would be useful to have a way to disable only these kinds of warnings without disabling all the other warnings.