Add more libm-test coverage of [a-c]* real functions.

Various libm functions have inadequate test coverage in libm-test.inc
/ auto-libm-test-in - failing to cover all the usual special cases
(infinities, NaNs, zero, large and small finite values, subnormals) as
well as a reasonable range of ordinary inputs and, where appropriate,
inputs close to the thresholds for underflow and overflow.

This patch improves test coverage for real functions [a-c]* (with the
expectation of adding more coverage for other functions later).

Tested x86_64 and x86 and ulps updated accordingly (and eight glibc
bugs and one C11 DR filed for issues found in the process).

	* math/auto-libm-test-in: Add more tests of acos, acosh, asin,
	asinh, atan, atan2, atanh, cbrt, cos and cosh.
	* math/auto-libm-test-out: Regenerated.
	* math/libm-test.inc (acosh_test_data): Add more tests.
	(atanh_test_data): Likewise.
	(ceil_test_data): Likewise.
	(copysign_test_data): Likewise.
	* sysdeps/i386/fpu/libm-test-ulps: Update.
	* sysdeps/x86_64/fpu/libm-test-ulps: Likewise.