Since constructors like gtk_radio_button_new_from_widget take an
instance of their type as the first argument, the gi scanner interprets
them as methods.
https://bugzilla.gnome.org/show_bug.cgi?id=661858
constructors which take an object of the same class as its first argument are
mis-detected as method call with "self" argument by the GIR scanner. Using the
new (constructor) annotation from bug 561264, mark some of them as proper
constuctors, so that you can call them with NULL as first argument from
bindings; in particular, this fixes gdk_window_new() and the
gtk_radio_button_new_with*() constructors.
This change does not introduce any functionality change, mostly
cosmtic cleanups, like re-linebreak when introduced annotations messed
up indentation or whitespace errors fixes.
In the current introspection data, the various gtk_radio_button_new_*
constructors take an existing group or widget. These all allow passing a NULL
widget or group list, so that it becomes easy to build a radio button list in a
loop (pass in None the first time, and the previously created button in all
other iterations).
Add the missing "allow-none" tag to the introspection data, so that this will
also eventually work for GIR users. NB that it does not actually work for some
constructors yet (like new_with_label_from_widget()) due to
https://bugzilla.gnome.org/show_bug.cgi?id=561264.
https://bugzilla.gnome.org/show_bug.cgi?id=635253
* this mirrors the committed change for gtk_radio_action_join_group in
commit 85b53969b2
* Due to object ownership issues it is impossible to correctly use
get_group/set_group from a GI binding
* join_group is safer because at the binding level it works with individual
GtkRadioButton objects and not with the list of objects that gets
modified in the library
https://bugzilla.gnome.org/show_bug.cgi?id=628935
