Rework the arguments to msdosarc: (dm)

Move specifying the source directory from -s to the first parameter.
Rename -p (peek) to -s (invoke shell).
Rename -n (archive name) to -a.
Add -r (replace archive).
Add -n (report short name conflicts).
Move the mkdosarc script into the DOS subdirectory. (dm)
Add the -h option to prologue.sh. (dm)
Add support for program parameters to prologue.sh. (dm)
dosinstall has now been superceded by mkdosarc. (dm)