GcalDateEntry and GcalTimeEntry now have a ::modified signal.
The internal attributes of both widgets were guint types, but since libical library has those values (day,month,hour) as int inside icaltimetype struct, I decided t move to gint in order to avoid compiler warnings, and ugly hidden things.
Initial approach. I really don't like the implementation, is kinda week. And it needs a lot of testing, localization kind of testing.