Get rid of 'gcc/omp-oacc-neuter-broadcast.cc:oacc_build_component_ref'

Clean-up for commit e2a58ed6
"openacc: Middle-end worker-partitioning support":
as of commit 2a3f9f65
"openacc: Shared memory layout optimisation", we're no longer
running into the vectorizer ICEs for '!ADDR_SPACE_GENERIC_P'.

	gcc/
	* omp-low.cc (omp_build_component_ref): Move function...
	* omp-general.cc (omp_build_component_ref): ... here.  Remove
	'static'.
	* omp-general.h (omp_build_component_ref): Declare function.
	* omp-oacc-neuter-broadcast.cc (oacc_build_component_ref): Remove
	function.
	(build_receiver_ref, build_sender_ref): Call
	'omp_build_component_ref' instead.