PeyloW, what's your current email address? I tried to contact you (same as GGN tried) exactly about your fastcall compiler -- we can't seem to figure out how to use the attributes, they are just ignored.
fastcall code seems to be generated only as whole, with -mfastcall.
Btw I've rebased your changes on the top of Vincent's so it's easily manageable: https://github.com/mikrosk/m68k-atari-mint-gcc/tree/gcc-4_6-mint-fastcall