Fix i386/x86_64 logl (sNaN) (bug 20227).

Fix i386/x86_64 logl (sNaN) (bug 20227).

The i386/x86_64 versions of logl return sNaN for sNaN input.  This
patch fixes them to add a NaN input to itself so that qNaN is returned
in this case.

Tested for x86_64 and x86 (including a build for i586 to cover the
non-i686 logl version).

	[BZ #20227]
	* sysdeps/i386/fpu/e_logl.S (__ieee754_logl): Add NaN input to
	itself.
	* sysdeps/i386/i686/fpu/e_logl.S (__ieee754_logl): Likewise.
	* sysdeps/x86_64/fpu/e_logl.S (__ieee754_logl): Likewise.
	* math/libm-test.inc (log_test_data): Add sNaN tests.