createEventNS as alternative to init*EventNS

An alternative to creating NS suffixed versions of all the existing init[*]Event methods would be to add a createEventNS() method and set the namespace (and potentially the compatibility flag mentioned in the previous message) at event creation time and use the existing init[*]Event methods to set the remaining parameters.

I think it would be very unlikely that the inability to change an event's namespace after creation would ever be a significant issue and it would reduce both the size of the spec and the number of interfaces that need to change for DOM L3.