Merge branch 'dist-refactor' into test-protocols

Merge branch 'dist-refactor' into test-protocols

* dist-refactor:
  cosmetics: remove obsolete comment
  tests: fix spurious failure with Solaris /bin/sh
  threaded-am: better serialization for required config files
  automake: refactor, break up 'require_file_internal'
  dist: separate auxiliary file instantiation from DIST_COMMON update
  refactor: rename a subroutine to a more proper name
  dist: truly always distribute files in AC_REQUIRE_AUX_FILE
  dist: simplify automake code accordingly to the previous changes
  dist: auxiliary files can be distributed from subdir Makefiles