add support arbitrary args

[janondrusek]

Assuming the default: basedir /. From man freebsd-update:

     -b basedir     Operate on a system mounted at basedir.  (default: /, or
                    as given in the configuration file.)

On systems where /etc/freebsd-update.conf overrides the basedir, this changes the default behavior.

[janondrusek]

Alternative would be to just pass "$@" like other commands do and remove the $# check.

[cedwards]

I think the alternative solution of using "$@" may be cleaner.