select tests, pselect tests: Refactor.

select tests, pselect tests: Refactor.

* tests/test-select.h: New file, extracted from tests/test-select.c.
(select_fn): New type.
(test, do_select, do_select_nowait, do_select_wait, test_tty,
test_connect_first, test_accept_first, test_pair, test_socket_pair,
test_pipe): Add my_select argument.
(test_function): Renamed from main. Add my_select argument.
* tests/test-select.c: Move most code to tests/test-select.h. Include
test-select.h.
* modules/select-tests (Files): Add tests/test-select.h.
* tests/test-pselect.c: Include test-select.h instead of test-select.c.
(my_select, main): New functions.
* modules/pselect-tests (Files): Add tests/test-select.h,
tests/macros.h, tests/signature.h.
(Depends-on): Remove select-tests. Add dependencies of test-select.h.
(configure.ac): Check for <sys/wait.h>.