Test rint and nearbyint with same inputs, in all rounding modes.

This patch arranges for rint and nearbyint to be tested by
libm-test.inc with the same inputs (previously each had some test
inputs the other didn't, although there was a lot of overlap as well),
and for nearbyint to be tested in all rounding modes where previously
it was only tested in round-to-nearest mode.  The expected results are
the same for each function, except that rint is expected to have
"inexact" exceptions for non-integer input and nearbyint is expected
not to have those exceptions.

Tested x86_64 and x86.

	* math/libm-test.inc (nearbyint_test_data): Include all tests used
	for rint.  Include results for all rounding modes.
	(nearbyint_test): Use ALL_RM_TEST.
	(rint_test_data): Include all tests used for nearbyint.