it looks good to me

Looks Good To Me

it can be part of the python option
Having those python extension inside the gdb port looks easier to me, at least for now
We'll use the portrevision to force the update of the package when only this external component got an update.
If we'll have daily releases, we'll re-consider the idea of a separate port

What do you think if, instead of creating a new port, just add those files to devel/gdb? It would solve any python/gdb dependencies and you'll get the .pyc managed for free.
We can use the gdb portrevision to manage libcxx updates..
I can prepare a patch to modify gdb if you're OK with it

LGTM
totally agree with John, about package naming: by default the package should be called gdb. The gdb-py36 should be used for the special case only.

I agree with John, about the suffix only for not default python version.
I need a bit of time, to properly test it.

That's solve the issue. I've completely forgot to test the different default python version...

tested and looks good to me

I guess it's fine to remove the qt4 version. I agree with @mat, I don't see any future for it.
Feel free to remove the qt4/kde4 version and keep only the qt5/kde5 one.
I won't be able to maintain the qt5 version, because I moved to i3, so no kde applications anymore for me

look good to me

Patch doesn't apply cleanly.

looks good to me