This feature is in Org 9, which is already required.

* doc/org/autcross.org, doc/org/autfilt.org, doc/org/compile.org,
doc/org/concepts.org, doc/org/csv.org, doc/org/dstar2tgba.org,
doc/org/genaut.org, doc/org/genltl.org, doc/org/hierarchy.org,
doc/org/hoa.org, doc/org/ioltl.org, doc/org/ltl2tgba.org,
doc/org/ltl2tgta.org, doc/org/ltlcross.org, doc/org/ltldo.org,
doc/org/ltlfilt.org, doc/org/ltlgrind.org, doc/org/ltlsynt.org,
doc/org/oaut.org, doc/org/randaut.org, doc/org/randltl.org,
doc/org/satmin.org, doc/org/setup.org, doc/org/tools.org,
doc/org/tut01.org, doc/org/tut02.org, doc/org/tut03.org,
doc/org/tut04.org, doc/org/tut10.org, doc/org/tut11.org,
doc/org/tut12.org, doc/org/tut20.org, doc/org/tut21.org,
doc/org/tut22.org, doc/org/tut23.org, doc/org/tut24.org,
doc/org/tut30.org, doc/org/tut31.org, doc/org/tut50.org,
doc/org/upgrade2.org: Simplify SRC block setups for sh, python and
C++.  Also fix a few typos and examples along the way.