Add more randomly-generated libm tests.

This patch adds more libm test inputs found through random test
generation to increase observed ulps on x86_64.

Tested for x86_64 and x86.

	* math/auto-libm-test-in: Add more tests of acosh, atanh, cbrt,
	cosh, csqrt, erfc, expm1 and lgamma.
	* math/auto-libm-test-out: Regenerated.
	* sysdeps/i386/fpu/libm-test-ulps: Update.
	* sysdeps/x86_64/fpu/libm-test-ulps: Likewise.