recent "upstream" debug additions

[GitMensch]

@nberth may want to inspect OlegKunitsyn/gnucobol-debug#145 and the overlap to the current integrated changes which seem to be also related to the tty option discussed with @emilienlemaire

[This issue should get the debugger label; and maybe it is reasonable to open issues in the submodule as well and move the debug label'd issues there?]

[nberth]

Some of the changes in the linked PR have already been integrated here. Still, I failed to make the linked PR work properly with submodules, so I implemented a different solution (although I took some inspiration from that PR), along with some code cleanups while I tried to understand the structure of this extension.

There may still be bugfixes in the linked PR that I did not integrate.

[GitMensch]

Just a reminder-ping to @nberth for cheecking and possibly closing this issue

[nberth]

Just a reminder-ping to @nberth for cheecking and possibly closing this issue

The code in this repository has diverged quite a bit from the upstream, so the linked PR is now definitely outdated.
The current state could benefit from being pushed upstream; but that would make a substantial PR anyways, so further changes to harden this extension could happen before that.