[Aarch64][SVE] Add copysign and xorsign support

This patch adds support for copysign and xorsign builtins to SVE. With the new
expands, they can be vectorized using bitwise logical operations.

I tested this patch in an aarch64 machine bootstrapping the compiler and
running the checks.

2019-01-09  Alejandro Martinez  <alejandro.martinezvicente@arm.com>

	* config/aarch64/aarch64-sve.md (copysign<mode>3): New define_expand.
	(xorsign<mode>3): Likewise.

2019-01-09  Alejandro Martinez  <alejandro.martinezvicente@arm.com>

	* gcc.target/aarch64/sve/copysign_1.c: New test for SVE vectorized
	copysign.
	* gcc.target/aarch64/sve/copysign_1_run.c: Likewise.
	* gcc.target/aarch64/sve/xorsign_1.c: New test for SVE vectorized
	xorsign.
	* gcc.target/aarch64/sve/xorsign_1_run.c: Likewise.

From-SVN: r267764