Introduce unsafe variants of basic messaging primitives

The send/nsend/sendChan family of primitives force serialisation, even
for local inter-process communication, to ensure full evaluation of the
message takes place prior to delivery. These new primitives skip that
step altogether, offering potentially better performance at the cost of
a less obvious evaluation strategy.
Update ProcessRing benchmark to support 'unsafe' sends
Simplify benchmark linking options
Test tracing more thoroughly, do not encode forwarded messages twice
Provide a note about our use of serialisation in `die'
Additional test case for monitoring a "live" node that subsequently dies