Add framework for using sparc VIS3 instructions, use it for copysign/signbit.

Add framework for using sparc VIS3 instructions, use it for copysign/signbit.

	* sysdeps/sparc/configure.in: New file.
	* sysdeps/sparc/configure: Generate.
	* configure.in (libc_cv_sparc_as_vis3): Substitute.
	* configure: Regenerate.
	* config.h.in (HAVE_AS_VIS3_SUPPORT): New.
	* config.make.in (have-as-vis3): New.
	* sysdeps/sparc/sparc32/sparcv9/Makefile (ASFLAGS-*): If VIS3 is
	available use -Av9d instead of -Av9a.
	* sysdeps/sparc/sparc64/Makefile: Likewise.
	* sysdeps/sparc/sparc32/sparcv9/fpu/multiarch/Makefile: New file.
	* sysdeps/sparc/sparc32/sparcv9/fpu/multiarch/s_copysign-vis3.S: New file.
	* sysdeps/sparc/sparc32/sparcv9/fpu/multiarch/s_copysign.S: New file.
	* sysdeps/sparc/sparc32/sparcv9/fpu/multiarch/s_copysignf-vis3.S: New file.
	* sysdeps/sparc/sparc32/sparcv9/fpu/multiarch/s_copysignf.S: New file.
	* sysdeps/sparc/sparc64/fpu/multiarch/Makefile: New file.
	* sysdeps/sparc/sparc64/fpu/multiarch/s_signbit-vis3.S: New file.
	* sysdeps/sparc/sparc64/fpu/multiarch/s_signbit.S: New file.
	* sysdeps/sparc/sparc64/fpu/multiarch/s_signbitf-vis3.S: New file.
	* sysdeps/sparc/sparc64/fpu/multiarch/s_signbitf.S: New file.