progs, libs: support _RANLIB overrides Much like we have per-target support for _AR and _LINK, add an _RANLIB override too. This allows selection of specific ranlib tools in case a non-standard archiver tool was forced. * bin/automake.in: Check for _RANLIB per-target settings. * doc/automake.texi: Document _RANLIB override. * lib/am/library.am: Change $(RANLIB) to $(%XLIBRARY%_RANLIB). * t/list-of-tests.mk: Add ranlib_override.sh. * t/ranlib_override.sh: New test. * NEWS: Mention new feature.