parallel-tests: allow each test to have multiple results With this change, we improve the code creating the `test-suite.log' global log and the console testsuite summary to make it able to grasp multiple results per test script. This is required in order to introduce the planned support for test protocols, like TAP and SubUnit, which can indeed run multiple tests per test script, each with its individual result. The implementation makes use of a custom reStructuredText field `:test-result:'. Note that no new documentation is added by this change; that is be left for follow-up changes. * lib/check.am ($(TEST_SUITE_LOG)): When processing .log files, recognize a report of a test's result only if it is declared with the custom `:test-result:' reStructuredText field placed at the beginning of a line. Extend and add explanatory comments. (recheck, recheck-html): Add explanatory comments. * lib/test-driver: Write an appropriate reStructuredText field `:test-result:' in the generated log file. Use a reStructuredText transition to better separate the test outcome report from the test script's registered output. Improve comments. * tests/test-driver-custom-xfail-tests.test: Adjust. * tests/parallel-tests7.test: Adjust. * tests/parallel-tests-empty-testlogs.test: New test. * tests/parallel-tests-recheck-override.test: Likewise. * tests/parallel-tests2.test: Extend and keep more in-sync with ... * tests/test-driver-custom-html.test: ... this new related test. * tests/test-driver-custom-no-html.test: New test. * tests/test-driver-custom-multitest.test: Likewise. * tests/test-driver-custom-multitest-recheck.test: Likewise. * tests/test-driver-custom-multitest-recheck2.test: Likewise. * tests/trivial-test-driver: New file, used by the last four tests above. * tests/Makefile.am (TESTS): Update. (EXTRA_DIST): Distribute `trivial-test-driver'. (test-driver-custom-multitest.log): Depend on `trivial-test-driver'. (test-driver-custom-multitest-recheck.log): Likewise. (test-driver-custom-multitest-recheck2.log): Likewise. (test-driver-custom-html.log): Likewise.