#12 Handle not passed to low-memory bios i/o vectors

[Roger Burrows]

The BIOS calls Bconstat(), Bconin(), Bcostat() & Bconout() are vectored through low-memory addresses starting at $51e. The args passed to the functions pointed to by these addresses should be the same as those passed to the BIOS functions themselves. This is true for Bconout(), but not for the other three functions. Although no program is known to be affected, this should be fixed for TOS compatibility. This will require a device handle argument for functions such as bconstat1(), bconin2(), bcostat3() etc, plus corresponding changes to some variable declarations etc.