by applying this patch, we would be able to extend freebsd-version's features to:
- print verbose information of the base system (using existing userland_version() function);
- print verbose information of the running kernel (using existing running_version() function);
- print verbose information from a slightly parsed output of what -qs (using existing kernel_version() function);
- update its manpage, mentioning __FreeBSD_version and the references to it.
this was tested against the following branches: