Merge branch 'ng/check' into ng/master

* ng/check:
  [ng] news: update w.r.t. recent changes in testsuite harnesses (TESTS based)
  [ng] doc: update w.r.t. recent changes in testsuite harnesses (TESTS-based)
  [ng] coverage: parallel-tests and dynamic $(TEST_EXTENSIONS) content
  [ng] cosmetics: improve comments and spacing in 'parallel-tests.am'
  [ng] check: support conditional $(TEST_EXTENSIONS)
  [ng] check: warn about dot-less $(TEST_EXTENSIONS) at make runtime
  [ng] check: be laxer in accepted $(TEST_EXTENSIONS)
  [ng] check: logic to define *LOG_DRIVER vars moved to generated Makefiles
  [ng] warns: don't report possible issues with '_DEPENDENCIES' variables
  [ng] refactor: merge check2.am into parallel-tests.am
  [ng] am: new make variable '$(am__handle_exeext)'
  [ng] check: unconditionally distribute test-driver
  [ng] check: warn about invalid TEST_EXTENSIONS at make runtime
  [ng] check: separate serial and parallel harnesses in distinct '.am' files
  [ng] check: move definition of console colors in its own '.am' fragment
  [ng] refactor: make '$am_config_aux_dir' available as a make variable
  [ng] am: implement $(am__tolower) and $(am__toupper)
  [ng] tests: get rid of an almost-obsolete test case (parallel-tests related)
  [ng] serial-tests: simplify automake-time preprocessing
  [ng] am: new private make variable $(am__all_progs)

diff --cc automake.in
Simple merge

diff --cc lib/am/header-vars.am
Simple merge