Update logging to use std::clog instead of syslog

Added log.h and log.cc, which define a streambuf that can take the
existing std::clog log stream and send the output to the system
logger, rather than sending it to stdout.  Then converted all existing
logging to use the stream-based logger.

Renamed the base server files from .c to .cc, since we're just going
to use C++ everywhere.  Updated the makefile to support these changes.

Also updated the TODO list.