m_spanningtree Change allocation of the specialized ProtocolInterface to be physically part of ModuleSpanningTree
Make the default ProtocolInterface instance part of class InspIRCd

The protocol module no longer has to delete it on load and construct it on
unload, only assign a new value to ServerInstance->PI
m_spanningtree Initialize TreeServer::UserCount for TreeRoot in its constructor
m_spanningtree Initialize boolean member variables in the constructor of the module