Fixed a few I/O handler adding/removing related bugs in the Intel PIIX/PIIX3, UMC UM8699F Super I/O chip, Sound Blaster DSP, and Realtek 8019AS codes;
The code in io.c now uses linked lists, I had to do this to properly fix the I/O handler mess with the Realtek RTL8019AS on the Award 430VX PCI (which was causing an emulator crash at POST).