Server startup structures now include a private data pointer which is passed

back to callback functions (e.g. lputs, thread_up, etc). This allows servers
to share the same callback functions, eliminating many nearly-identical
functions. This was able to shave quite a bit of redundant code from ntsvcs.c.
This feature is not utilized in sbbs (sbbscon.c) or sbbsctrl (mainformunit.cpp).