Properly support all events in trace files and clean up a bit.

In particular, use both message and range type to identify events so
that we can get rid of the messy type aliasing.

Task-number: QTBUG-36953
Change-Id: I691a7501aa285f78f7ce5b7017ef50628f44fcf7
Reviewed-by: Simon Hausmann <simon.hausmann@digia.com>