1. the UWOBO_LOG_FILE environment variable semantics changed. It is now
used in the following way: $UWOBO_LOG_FILE.pid.log
2. when the log file can not be opened, UWOBO used to crash. Instead,
it now goes on and a nice error message is printed on the stderr
(but, unfortunately, it is not given back to the user, since the
error is raised in a new process and it can not be read back from
the logfile!)