Transition from 5.1-RELEASE-p10 to 5.3-BETA2

[Achilleus Mantzios]

Hi, after make buildworld,make buildkernel, make install kernel
i rebooted single-user, just to find out that
ls, mount, etc.. gave
ls exited with signal 12,
bad system call.

After i rebooted with the old 5.1 kernel and did make buildkernel
*with* COMPAT_FREEBSD4, i could reboot single user with
5.3 and run ls,mount, etc... just fine.

What has COMPAT_FREEBSD4 has to do, since i *didnt* have it in my 
5.1-RELEASE-p10, and no FreeBSD 4.x programs were run?

Another point that maybe should be addressed in docs (UPDATING) is that 
when rebooting
single user / is mounted ro, so mergemaster -p cannot write to 
/etc/master.passwd, groups.
-- 
-Achilleus