Add a better security model.  It would be nice to have 3.5's ability to check
every line of an RPC as it is executed rather than a one-time check.

Look into porting DP's serial port routines to Tcl's internal routines.  Serial
ports are SUCH a mess in Unix that it's not worth the time to maintain our own
drivers when they seem to be of marginal use, IMHO.

HP9 fails TCP buffer tests.  I don't think the system will allow a socket
    buffer < 8192 bytes.

