Fix the APU half-carry bug, which may be audible.
globals.cpp: Get rid of A1, A2, A3, A4, W1, W2, W3, W4, Int8, Int16, Int32, Work8, Work16, Work32, Ans8, Ans16, Ans32.
Run the opcode as a tail call from the address calculation. This cuts on the needed return instructions.
Pass the opcode address as a parameter; this keeps it in a register most of the time and avoids memory stores.
SNES Open Bus is a quirk of the memory subsystem that allow reads of invalid addresses to return the last byte read from memory. However, it is seldom needed by a game, and it costs 1 to 3 MIPS instructions per SNES instruction to emulate.
If you need SNES Open Bus, you can remove -DNO_OPEN_BUS from the Makefile.
With the MIPS instruction cache, this means that two consecutive SNES CPU instructions using e.g. the same addressing style or the same opcode have a chance that the second one will use the first one's code and that it will be cached.
