io/router: [API] make SemanticID a uint, not uint64

4 billion semantic IDs should be enough for everyone.

Signed-off-by: Elias Naur <mail@eliasnaur.com>

io/router/router.go

@@ -88,7 +88,7 @@ const (
 // SemanticID uniquely identifies a SemanticDescription.
 //
 // By convention, the zero value denotes the non-existent ID.
-type SemanticID uint64
+type SemanticID uint
 
 type handlerEvents struct {
 	handlers  map[event.Tag][]event.Event