RFC: side effects of fixing loader_conf_files handling

[Luigi Rizzo]

hi,
in some recent commits to HEAD and stable/7 i fixed the handling
of loader_conf_files so that it behaves as always intended and
documented in loader.conf(5):

    ...
    loader_conf_files
                   Defines additional configuration files to be processed
                   right after the present file.

Previously, the check for new assignments was incorrect, and it happened
to ignored assignments which did not result in a buffer reallocation
by the Forth interpreter (essentially, any string not longer
than the current one was ignored).

An annoying side effect of the fix is that now people who (mistakenly)
copied /boot/defaults/loader.conf into /boot/loader.conf (and
possibly edit it), now create a loop because their /boot/loader.conf
now contains

    loader_conf_files="/boot/device.hints /boot/loader.conf /boot/loader.conf.local"

which is not just a pure assignments.

Never mind the fact nobody ever recommended to copy the file and
then modify the copy, there seem to be several people who do this
(and do the same for /etc/defaults/rc.conf).

I think we should remove the use of loader_conf_files=...
from /boot/defaults/loader.conf, partly to prevent this kind
of bugs, and partly because it is nice to have only "pure assigments"
in this file.

If there are no objections, i will look at how to do it. 
Probably this requires putting the initial list of files 
somewhere else, probably in /boot/loader.rc after the 

        include /boot/loader.4th

statement.

Comments ?

        cheers
        luigi