parallel-tests: avoid command-line length limit issue. * automake.in (handle_tests): New argument $makefile, new substitution %MAKEFILE%. (generate_makefile): Adjust. * lib/am/check.am [%?PARALLEL_TESTS%] (check-TESTS): Pass sanitized TEST_LOGS value as makefile snippet on standard input to $(MAKE), to avoid exceeding the command line limit on w32 (MSYS). * NEWS: Update. Report by Bob Friesenhahn.