run-tests: introduce 'warned' as test result While running, a test resulting in 'warned' is shown as '~'. Test results with state warned are listed between the skipped and the failed tests. Example: Skipped test-revert-flags.t: missing feature: executable bit Skipped test-inotify-lookup.t: missing feature: inotify extension support Warned test-something.t: output changed Failed test-largefiles.t: output changed Failed test-subrepo.t: output changed # Ran 11 tests, 2 skipped, 1 warned, 2 failed. The test result "warned" will be used in later patches.