[Gtk-sharp-list] ToggleButton doc update

[John Luke]

Hello,

Here is an updated version of gtk-sharp/doc/en/Gtk/ToggleButton.xml

It adds small examples for some of the constructors and properties, and
fixes a typo. Can someone commit this if it is OK?

And now a couple questions to help me in my doc efforts:

1. Are examples in VB.net wanted as well, or should we concentrate on C#
for now and add VB later?

2. Does the current version of monodoc handle all the <see cref=""/> and
<see langword=""/> elements?

3. Should there be a <see cref="E:SomeEvent"/> type?

4. Is there a place to check if anyone is working on documenting a
class, such as the Bugzilla bug that no longer seems to be updated?

Thanks,
John Luke