Merge branch 'master' into testsuite-work

Merge branch 'master' into testsuite-work

Commits merged from master:
 - test defs: new functions to analyze configure help screen
 - warnings: fix buglets for portability warnings
 - tests: extend tests on 'extra-portability' warning category

Extra edits to the testsuite:
* tests/extra-portability.test: Use `$am_original_AUTOMAKE'
instead of the obsolete `$original_AUTOMAKE'.
* tests/extra-portability3.test: Likewise.
* tests/list-of-tests.mk: Update.