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.
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.