Fix incorrect usage of gtk_radio_button_new_with_label()/gtk_radio_button_get_group();

Fix incorrect usage of gtk_radio_button_new_with_label()/gtk_radio_button_get_group();
Use gtk_radio_button_new_with_label_from_widget().

Essentially: gtk_radio_button_get_group() must be called after each gtk_radio_button_new...()
before using the 'group' GSList pointer in another call to gtk_radio_button_new...().

In these cases the incorrect usage appears to only have resulted in allowing multiple
radio buttons to be activated simultaneously.

(In at least one case elsewhere, the incorrect usage resulted in a Wireshark crash).

git-svn-id: http://anonsvn.wireshark.org/wireshark/trunk@37869 f5534014-38df-0310-8fa8-9805f1628bb7