Add more tests of acos.

This patch adds some randomly-generated tests of acos that are
observed to increase ulps on x86_64.

Tested for x86_64 and x86 and ulps updated accordingly.

	* math/auto-libm-test-in: Add more tests of acos.
	* math/auto-libm-test-out: Regenerated.
	* sysdeps/i386/fpu/libm-test-ulps: Update.
	* sysdeps/x86_64/fpu/libm-test-ulps: Likewise.