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).
The UMC UM8669F's reset function now make sure the FDC pointer does not get lost, should fix the segmentation fault on reset;
The Winbond W83877F's reset function now zeroes the registers before setting the default values.
Merged floppy.c and fdd.c and renamed floppy_*.c (the floppy image format handlers) to fdd_*.c;
Reading the AT or PS/2 keyboard controller status no longer clears the transmit timeout bit, fixes error 8601 (mouse error) on the IBM PS/2 Model 80;
MMU translate and DMA physical reads and writes now go through _mem_exec instead of directly to ram[], should fix the last remaining problems with remapped mappings;
Implemented the Sound gain dialog;
Added the resource for the "New floppy image" dialog and the needed functions for the functionality of exporting the currently mounted floppy image as 86F, both of which should be finished in the next commit;
Applied the CD-ROM fixes from the PCem commit;
Added the "Keep ratio" option for full screen stretch.
IBM.H is gone, video stuff re-organized. Keyboard stuff reorganized.
Machines that have their own video, mouse and/or keyboard now have all this in their machine file.
Fixed and other cleanups here and there.
