Merge branch 'ab/doc-lint'

Merge branch 'ab/doc-lint'

Dev support.

* ab/doc-lint:
  docs: fix linting issues due to incorrect relative section order
  doc lint: lint relative section order
  doc lint: lint and fix missing "GIT" end sections
  doc lint: fix bugs in, simplify and improve lint script
  doc lint: Perl "strict" and "warnings" in lint-gitlink.perl
  Documentation/Makefile: make doc.dep dependencies a variable again
  Documentation/Makefile: make $(wildcard howto/*.txt) a var