svc - Implement more features

svc - Implement more features

* All stdout/stderr output now goes to a pipe and a pipe buffering thread
  to read it into a circular buffer as well as write it to the log file.

  The program is now able to retain ~8KB worth of output in its circular
  buffer whether there is a log file attached to the service or not.

* When /dev/null is specified as the log file, short-cut the descriptor to -1
  instead of actually writing to /dev/null.

* log, logf, and tailf directives now work.

* Properly escape '.' on a line by itself for all buffered data dumped
  over a remote link (allowing logs to contain our command response
  terminator).

* Implement -f (foreground option) and clean-up descriptor initialization.

* Implement -s (sync on exit)