aarch64: Reimplement vaddlv* intrinsics using builtins

aarch64: Reimplement vaddlv* intrinsics using builtins

This patch reimplements the vaddlv* intrinsics using builtins.
The vaddlv_s32 and vaddlv_u32 intrinsics actually perform a pairwise
SADDLP/UADDLP instead of a SADDLV/UADDLV but because they only use
two elements it has the same semantics.

gcc/ChangeLog:

	* config/aarch64/aarch64-simd-builtins.def (saddlv, uaddlv):
	Define builtins.
	* config/aarch64/aarch64-simd.md (aarch64_<su>addlv<mode>):
	Define.
	* config/aarch64/arm_neon.h (vaddlv_s8): Reimplement using
	builtin.
	(vaddlv_s16): Likewise.
	(vaddlv_u8): Likewise.
	(vaddlv_u16): Likewise.
	(vaddlvq_s8): Likewise.
	(vaddlvq_s16): Likewise.
	(vaddlvq_s32): Likewise.
	(vaddlvq_u8): Likewise.
	(vaddlvq_u16): Likewise.
	(vaddlvq_u32): Likewise.
	(vaddlv_s32): Likewise.
	(vaddlv_u32): Likewise.
	* config/aarch64/iterators.md (VDQV_L): New mode iterator.
	(unspec): Add UNSPEC_SADDLV, UNSPEC_UADDLV.
	(Vwstype): New mode attribute.
	(Vwsuf): Likewise.
	(VWIDE_S): Likewise.
	(USADDLV): New int iterator.
	(su): Handle UNSPEC_SADDLV, UNSPEC_UADDLV.

gcc/testsuite/ChangeLog:

	* gcc.target/aarch64/simd/vaddlv_1.c: New test.