doscmd heavily depends on struct sigcontext which luckily is mostly passed
between functions as usion regcontext_t. By redefining union regcontext_t in
terms of mcontext_t almost all bases are covered.
It also seems to me that doscmd was in a transitional state. The redundant
definitions made it difficult to get a clear overview and could easily cause
oversight. To make sure my changes were ok, I went as far as to complete the
transition. It was not exactly necessary, but I expect to have to come back
here some more ("whistle" if I'm wrong :-).
o When reporting a int21 function we don't know about yet, report
AH as the major and AL as the minor, as opposed to reporting AL
as the major.
o Add support for 21:44:7: ioctl check output status. We
optimistically say that output is always ready.
o Add half support for 21:23: get file size. We always now return
failure. This function isn't supported, according to the interrupt
list, by the DOS box in windows, so I don't feel too bad.
o Remove init printf
o Don't set optind from return value for do_args. getopt has already
done this.
o Bump EMS memory from 1M to 10M (this really should be a command line
option).
o Open /dev/null when requested to open emmxxxx0 to allow many programs
checking to see if EMS is installed to find it.
o Route int67 to ems_entry to allow EMS to be used when DOS is emulated
as well as when DOS is booted. This may obviate the need for the
driver doing anything at all in a really booted situation and won't
hurt that case.
I can now run the DOS program I'm interested in running with enough
EMS memory that its "advanced" functions are enabled and working.
o Make the dos emulation treat c: and C: the same way. Sourcer was doing
a chdir("c:\\") rather than a chdir("C:\\");
o use drlton() in all places where we used to use -'A' so that we're always
case independent.
o use drntol() in all places where we used to use + 'A' for similar reasons
