Gtk::ColorChooser::get_rgba(): Add documentation
gtk/src/enums.hg: Remove documentation of enums, gmmproc adds it
Gtk::Switch: Fix _IGNORE_SIGNAL("activate")
Gtk::ToolItem: Add class docs. Add unset_proxy_menu_item()

* gtk/src/toolitem.[hg|ccg]: The gtk_tool_item_set_proxy_menu_item() docs
don't tell whether the menu_item argument can be NULL, but the gtk+ code
explicitly allows it, and the create-menu-proxy signal docs mention this
case. An unset method seems appropriate.