rint* tests: More tests.

rint* tests: More tests.

* tests/test-rint.h: New file, partially extracted from
tests/test-rintl.c.
* tests/test-rint.c: Include test-rint.h.
(main): Invoke test_function.
* tests/test-rintf.c: Include test-rint.h.
(main): Invoke test_function.
* tests/test-rintl.c: Include test-rint.h.
(main): Invoke test_function.
* modules/rint-tests (Files): Add tests/test-rint.h, tests/randomd.c.
(Makefile.am): Add randomd.c to test_rint_SOURCES.
* modules/rintf-tests (Files): Add tests/test-rint.h, tests/randomf.c.
(Makefile.am): Add randomf.c to test_rintf_SOURCES.
* modules/rintl-tests (Files): Add tests/test-rint.h, tests/randoml.c.
(Makefile.am): Add randoml.c to test_rintl_SOURCES.