Use talloc, not malloc
Clean up listener code

After years of ifdef-hell.  Move the names && type-specific
structure sizes into a common structure.  This is in preparation
(once more) for plug-in protocols
No longer need module_struct != module_name
Move VMPS into a plug-in library

A bit of a hack for now, but we're on the way to moving
all of the protocols into plug-in libraries.  It should make
the server core a lot simpler.  And easier to add new protocols.