* tests/Makefile.am (TESTS_ENVIRONMENT): Export EXEEXT.
(test_programs): New.  Run pipeconnect for Windows, too.
(check_SCRIPTS): New.
(TESTS): Now, it's test_programs and check_SCRIPTS.
(noinst_PROGRAMS): Not including check_SCRIPTS.
(tests/fdpassing-socket.sh): New, to test socket connection.
* tests/fdpassing.c: Include socket connection test.
* tests/pipeconnect.c: Fix for Windows.