that has a callback to the user that tells them when a listening port
has been opened and what the port number is.

than by reference.

fixed a few subtle race conditions and now the tool seems to work
robustly.

functions.

times.

optional arguments to the worker function.

 - Simplified and optimized the running_stats implementation
 - Clarified the spec a little

from compiling.

Turns out this causes path conflicts on some systems.