aarch64: Use using directives to inherit constructors

aarch64: Use using directives to inherit constructors

Now that the codebase is C++11, we can use using directives
to inherit constructors from base classes.

gcc/
	* config/aarch64/aarch64-sve-builtins-functions.h (quiet)
	(rtx_code_function, rtx_code_function_rotated, unspec_based_function)
	(unspec_based_function_rotated, unspec_based_function_exact_insn)
	(unspec_based_fused_function, unspec_based_fused_lane_function):
	Replace constructors with using directives.
	* config/aarch64/aarch64-sve-builtins-base.cc (svcnt_bhwd_pat_impl)
	(svcreate_impl, svdotprod_lane_impl, svget_impl, svld1_extend_impl)
	(svld1_gather_extend_impl, svld234_impl, svldff1_gather_extend)
	(svset_impl, svst1_scatter_truncate_impl, svst1_truncate_impl)
	(svst234_impl, svundef_impl): Likewise.
	* config/aarch64/aarch64-sve-builtins-sve2.cc
	(svldnt1_gather_extend_impl, svmovl_lb_impl): Likewise.
	(svstnt1_scatter_truncate_impl): Likewise.