RFC: Dealing with version-specific docs

[Gabor Kovesdan]

Hi,

as you may know, the printed edition of FreeBSD Handbook is being 
worked. In our current Handbook version, we have version-specific 
information for different major releases, while the printed edition 
shall concentrate on 9.X. We cannot just drop the parts that detail 
older releases since they haven't yet reached EOL and there are people 
out there still using these. So we have to deal somehow with this 
situation. Fortunately, DocBook provides a mechanism, called profiling, 
which we could use. It would also be beneficial for later cleanup work 
since finding outdated information that has to do with unsupported 
releases always requires big effort. I've made a draft about how it 
could be done in a practical way:
https://wiki.freebsd.org/VersionSpecificDocs

Please read it and if you have doubts, concerns or better suggestions, 
please share them.

Thanks in advance,
Gabor