[AArch64] Add vcvt(_high)?_f32_f16 intrinsics, with BE RTL fix

[AArch64] Add vcvt(_high)?_f32_f16 intrinsics, with BE RTL fix

gcc/:

	* config/aarch64/aarch64-simd.md (aarch64_simd_vec_unpacks_lo_<mode>,
	aarch64_simd_vec_unpacks_hi_<mode>): New insn.
	(vec_unpacks_lo_v4sf, vec_unpacks_hi_v4sf): Delete insn.
	(vec_unpacks_lo_<mode>, vec_unpacks_hi_<mode>): New expand.
	(aarch64_float_extend_lo_v2df): Rename to...
	(aarch64_float_extend_lo_<Vwide>): this, using VDF and so adding V4SF.

	* config/aarch64/aarch64-simd-builtins.def (vec_unpacks_hi): Add v8hf.
	(float_extend_lo): Add v4sf.

	* config/aarch64/arm_neon.h (vcvt_f32_f16, vcvt_high_f32_f16): New.
	* config/aarch64/iterators.md (VQ_HSF): New iterator.
	(VWIDE, Vwtype, Vhalftype): Add V8HF, V4SF.
	(Vwide): New mode_attr.

From-SVN: r227551