pvm_exit — tells the local pvmd that this process is leaving PVM.
[info] = pvm_exit()
pvm_exit tells the local pvmd
that this process is leaving PVM.
This routine does not kill the process, which can continue to
perform tasks just like any other serial process.
pvm_exit should be called by all PVM processes before
they stop or exit for good. It must be called
by processes that were not started with pvm_spawn.