Add more sNaN tests (most remaining real functions).

This patch adds tests of sNaN inputs to more functions to
libm-test.inc.  This covers the remaining real functions except for
scalb, where there's a bug to fix, and hypot pow fmin fmax, where
there are cases where a qNaN input does not result in a qNaN output
and so sNaN support according to TS 18661-1 is more of a new feature.

Tested for x86_64 and x86.

	* math/libm-test.inc (snan_value_ld): New macro.
	(isgreater_test_data): Add sNaN tests.
	(isgreaterequal_test_data): Likewise.
	(isless_test_data): Likewise.
	(islessequal_test_data): Likewise.
	(islessgreater_test_data): Likewise.
	(isunordered_test_data): Likewise.
	(nextafter_test_data): Likewise.
	(nexttoward_test_data): Likewise.
	(remainder_test_data): Likewise.
	(remquo_test_data): Likewise.
	(significand_test_data): Likewise.
	* math/gen-libm-test.pl (%beautify): Add snan_value_ld.