* mk/default.mk: Add default for new variable BTEST_RE to select all
tests. (BTEST_OB_LANGUAGES): Remove sh (always needed, as
emacs-lisp) and add comment for ruby. (BTEST): Use BTEST_RE to
select tests from the test suite. Reorganize pre-loading of Org,
Babel, Ox and babel languages into a known clean environment.
* mk/targets.mk (CONF_TEST): Add BTEST_RE to the output of
config-test.
* testing/org-batch-test-init.el: New file. Remove all traces of any
Org built into Emacs or otherwise present in the environment so it
can not be picked up spuriously during testing or conceal errors in
the Org version under test.
* testing/org-test.el (org-test-run-batch-tests): Showtest selection
in messages. (org-test-run-all-tests): Update ID locations.