Misc Fixes

[Juan Pablo Ugarte]

Hi Tristan, I did not had time to browser the bug list and see if this
fixes belong to a bug, or even report them.

Anyways, here is a summary of things I notice and been fixing

GtkBox orientation bug: the internal vbox of dialogs gets as default a
horizontal orientation.
We should not apply catalog default values to internal widgets, right?

GtkBox size property broken: you cant decrease the size in an internal
vbox

GtkButton stock property is not being set properly on internal dialog
buttons.

GtkDialogs extra placeholders: most of the dialogs are showing extra
placeholders in my internal-child-support branch, this is probably a
regression