If the execution of the cnet event currently being handled
by the current node is being traced,
a call to CNET_trace() will format and print the requested output to
cnet's trace stream.
If execution is not currently being traced,
a call to CNET_trace() has no effect and, so, may be safely left
in a protocol's source code.
The arguments to CNET_trace() are just like those of the
standard-C function printf(),
and all of the standard formatting sequences (introduced with %)
are supported.
If the current simulation has registered a tracefile
(via its topology file),
the output of CNET_trace() will always be appended to that file.
When running under the Tcl/Tk graphical interface,
the output of CNET_trace()
also appears in a graphical pane below the main network "map".
When running without the Tcl/Tk graphical interface,
the output of CNET_trace()
also appears on cnet's stderr output stream.
