Improved implementation of transport-independent rpc (ti-rpc).

changes introduced in the ntirpc library include:
* bi-directional operation.
* full-duplex operation on the tcp (vc) transport.
* thread-safe operating modes:
* new locking primitives and lock callouts (interface change).
* stateless send/recv on the tcp transport (interface change).
* flexible server integration support.
* event channels.