Fix i386 asinhl (sNaN) (bug 20218).

The i386 version of asinhl returns sNaN (without raising any
exceptions) for sNaN input.  This patch fixes it to add non-finite
arguments to themselves, so that "invalid" is raised and qNaN
returned.

Tested for x86_64 and x86.

	[BZ #20218]
	* sysdeps/i386/fpu/s_asinhl.S (__asinhl): Add non-finite argument
	to itself.
	* math/libm-test.inc (asinh_test_data): Add sNaN tests.