Merge branch 'je-silent' into next * je-silent: Rename `silent' mode to `silent-rules' mode. `silent' mode unconditionally overrides portability-recursive. Drop extra line from compile rules when `silent' is not used. Keep `--silent-rules' across triggered automake reruns. Provide variables for silencing of user rules. Redo variable naming for `silent' machinery. Let -Wportability turn on/off the portability-recursive channel. New automake command line option `--silent-rules'. Documentation and tests for the `silent' option. Implement `silent' build rules. New channel `portability-recursive'.