buildroot

manual: various fixes

Various consistency and correctness improvements.

Also removing some sentences that are not or no longer relevant.

Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Acked-by: Samuel Martin <s.martin49@gmail.com>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>