Plug-in debugger support for gud.el

[Dave Abrahams]

I just rebased against HEAD the set of changes to gud.el that the LLDB project
created in 2010: http://j.mp/gud-lldb

I’d submit it, but I’m not the author of these changes and I suspect there
would be licensing problems.  I also don’t love the idea of maintaining a
patchset to a standard emacs package.

So I was thinking, wouldn’t it be great if gud.el was factored in such a way
that debugger back-ends could be added as plug-ins?  Then, presumably,
someone could maintain a smaller lldb.el package that, when loaded, adds
lldb support to gud.

Thoughts?