Add floppy controllers to "drives" list also.

Add floppy controllers to "drives" list also.

The Drives.drives list now contains floppies, harddrives, and cdroms.
Add mapping table for external/internal drive ids for floppies.
Rename CONFIG_FLOPPY_SUPPORT to CONFIG_FLOPPY (for consistency).
Be consistent with "driveid" and "floppyid" variable names.
Replace switch statements of drive parameters into a global array.
There are some externally visible changes with this patch:
  - Some calls will now return EPARAM instead of ETIMEOUT (or ECHANGED)
  - floppy_1301/1308 are now only available when regs->dl is valid
  - floppy_1308/1315 return EPARAM on invalid drives