The industry convention for mouse driven menu options is for them
to be activated when two conditions are met:
* a button down event occurs with the pointer inside the option, and;
* a button up event occurs with the pointer inside the option.
This issue was already solved on the PaletteMenuItem,
but the EventIcon have the same problem. This change add a 'activate' event,
that control that the two conditions are meet.
The code in Sugar need use this event instead of button-release-event.
Gonzalo Odiard
a19cf9ed27