Simplify the event types

Dedicated classes for parameterless event types and pimpl in
event classes is overkill. Following the QEvent conventions,
some "int/void* reserved" can be added if felt necessary.

Change-Id: Ie5536dd8c68333be07ebae13ac5c74129236e9df
Reviewed-by: Jake Petroules <jake.petroules@petroules.com>
Reviewed-by: Joerg Bornemann <joerg.bornemann@digia.com>