I added convenience macros for check and radio, easing discoverability
in C.
This will avoid C# issues such as:
lib/elementary/elm_pan.eo.cs(14,23): warning CS0108: `elm.Pan.CHANGED'
hides inherited member `efl.Gfx.CHANGED'. Use the new keyword if hiding
was intended
lib/efl/interfaces/efl_gfx.eo.cs(24,23): (Location of the symbol related
to previous warning)
Since nstate is not a legacy widget, I can safely change the event name
and the test case.