Merge branch 'master' into testsuite-work

Merge branch 'master' into testsuite-work

* master:
  tests: check portable fd redirection in TESTS_ENVIRONMENT
  news: update w.r.t. introduction of AM_DISTCHECK_CONFIGURE_FLAGS
  tests: optimize tests on primary/prefix mismatch for speed
  Warnings about primary/prefix mismatch fixed and extended.
  maintcheck: DISTCHECK_CONFIGURE_FLAGS can be defined on make cmdline
  distcheck: add support for AM_DISTCHECK_CONFIGURE_FLAGS
  docs: better documentation for silent make rules