make some samples GTK3 ready
Merge pull request #141 from Mazwak/master

Various fixes for gtk3 demo

Patch by Simon Arnaud. Thanks!!!
update
Merge pull request #142 from detlefreichl/master

Make some samples GTK3 ready

Patch by Detlef Reichl. Thanks!!!
gtk3: remove current directory restriction

We can run gtk-demo in any directory.
gtk3: fix indent
gtk3: use meanigful name

Script is more self-descriptive rather than fn (file name?).
gtk3: remove trailing spaces
gtk3: use spaces for indent
gtk3: use spaces for indent
gtk3: remove code for Ruby 1.8

We don't support Ruby 1.8.
gtk3: untabify
gtk3: use symbol instead of constant
gtk3: untabify
gtk3 add Gtk::TreeModel.get_path
Merge pull request #143 from detlefreichl/tree_model_get_path

gtk3 add Gtk::TreeModel.get_path

Patch by Detlef Reichl. Thanks!!!
gtk3: use more self-descriptive name

"ret" is too general.
gtk3-demo: Fix changedisplay.rb

Mostly fixed. Segfaults when clicking on 'change'.
Both 1.9.3-p392 and 2.0.0-p0