[rfa] doc/gdbint.texinfo: update commands for release tarball

[Michael Elizabeth Chastain]

> I cut/paste these sequeces when doing a release (which is why they keep 
> changing) so having just the new one there would break me doing a 
> re-spin of the current branch :-)

Mmm, shouldn't you cut/paste out of doc/gdbint.texinfo in the
branch when you are spinning the branch?

> For the moment, I think clone it.  (but add a cindex?)

I'm willing to clone it if I can't convince you to look in the right
place.  :)

It just really frustrated me yesterday when you said 'there's a problem
in the snapshot tarball' and I could not make a snapshot tarball.
That's why I am keen on this.

Michael C