[Bug-gnubg] Updating to gtk3

[Christian Anthon]

Hi all,

I'm currently going through the code to see what needs to be done to
update the code to current gtk2 standards, which will make porting to
gtk3 much easier when the time comes. Also some of the deprecated gtk
functions (in particular clists used for some of the table widgets
that we have) doesn't work to well already now.

Not all of the changes that needs to be made will be compatible with
earlier versions of gtk. In particular all access to semi public
widget data needs to use getters/setters not available until now. This
will impact users of legacy linux and other *nix based distributions,
like for example debian and RHEL/Centos. I'm going to ignore that for
now as we should be able to backport most of the needed changes if we
feel we want to support these old distributions.

I'm going to put a note in the ChangeLog if I believe that a change
warrants testing. So early checkers please report back.

Christian.