* Use make variables instead of hard coding commands, paths, and
options.
* Wrap some long lines.
* Replace shell loops with make for loops, etc.
PR: docs/31132
Submitted by: Cyrille Lefevre <clefevre@citeweb.net>
fix the case where the release notes are not exactly three levels
below in "something/something-else/doc" (if that's not the case,
doc.relnotes.mk would be unable to find the right path to the doc/
tree).
