XmlprotocolSource* Applicative part of the interface of CoqIde calls to Coq
* Protocol version
By default, we still output messages in Richpp so we are compatible with 8.6, however, 8.7 aware clients will want to set this to Ppcmds
* XML data marshalling
* Debug printing
Classification of messages handled by different mechanisms
* Serialization of feedback
* Serialization of debugger output