Lack of underlined accelerators in stock buttons

[Federico Mena Quintero <federico ximian com>]

When you create a message box or dialog box with stock
yes/no/ok/cancel/whatever buttons, they do not have underlined
accelerators.  So you cannot simply press "Y" to confirm a question
dialog, for example.

We need a way for gnome_dialog_append_button() and friends to ask the
gnome-stock framework for which accelerator to use for a particular
button name.  And then gnome-stock needs to create an underlined label
and all that.

Thoughts?

  Federico