Enable named-checkzone and named-compilezone to take input from stdin

Enable named-checkzone and named-compilezone to take input from stdin

If a filename (the last argument) is not provided for named-checkzone or
named-compilezone, or if it is a single dash "-" character,
zone data will be read from stdin.

Example of invocation:
cat /etc/zone_name.db | named-compilezone -f text -F raw \
    -o zone_name.raw zone_name