I've got stdio.asm to the point where it's pretty useful, I've got a hex and decimal print-to screen and print-to-buffer routines working. Remaining routines are print signed decimal, 32-bit support and formatted output (ex: 0x%04X)

I found an annoying bug in the compiler, it seems to do lazy symbol matching when processing expressions. a line like "bl @sprintf" seems to be processed as if it were "bl @sp", resuling in a "register value used as expression" error.