Fixed setDeliveryPersistent javadoc

Issue: SPR-3983
SourceHttpMessageConverter's supports implementation needs to check for StAXSource

Issue: SPR-11341
Polish
Add DestinationUserNameProvider interface

The interface is to be implemented in addition to
java.security.Principal when Principal.getName() is not globally unique
enough for use in user destinations.

Issue: SPR-11327
Use DestinationUserNameProvider with @SendTo

Issue: SPR-11327
Fix SerializableTypeWrapper equals() performance

Change SerializableTypeWrapper proxies to directly call equals() methods
on the underlying Type, rather than possibly generating more wrappers.

This should help to improve performance, especially as the equals()
method is called many times when the ResolvableType cache is checked.

Issue: SPR-11335
Encode user names in user destanations

Issue: SPR-11302