Fixes and extra functionality for emulators/doscmd

A year or so ago I emailed these patches to the maintainer
and didn't get any feedback. Just rediscovered them so
figured I should submit them before they get lost...

patch-bioscursor
Fixes the BIOS cursor handling so that programs such as the
DOS edit.com and qbasic.exe work correctly

patch-desqview-timeslice
Allows INT15 timeslicing so that programs which support it
can avoid 100% CPU utilization

patch-quitemode
Adds a -Q option which suppresses all video IO. Also helps
optimize the input behavior especially when polling for
input.

patch-fossil-support
Adds a -F option which enables support for FOSSIL IO using stdio.

PR: ports/114615
Submitted by: Stephen Hurd <shurd@sasktel.net>
Approved by: maintainer timeout