rint tests: More tests.

rint tests: More tests.

* tests/test-rint.c: Include <float.h>, <stdio.h>, isnand-nolibm.h,
minus-zero.h, infinity.h, nan.h.
(main): Skip the test if the current rounding mode is not standard. Add
tests for negative numbers, minus zero, infinity, NaN.
* modules/rint-tests (Files): Add tests/minus-zero.h, tests/infinity.h,
tests/nan.h.
(Depends-on): Add isnand-nolibm.