re PR c++/71257 (OpenMP declare simd linear with ref modifier doesn't accept references to non-integer/non-pointer)

	PR c++/71257
	* tree-vect-stmts.c (vectorizable_simd_clone_call): Handle
	SIMD_CLONE_ARG_TYPE_LINEAR_REF_CONSTANT_STEP like
	SIMD_CLONE_ARG_TYPE_LINEAR_CONSTANT_STEP.  Add
	SIMD_CLONE_ARG_TYPE_LINEAR_VAL_CONSTANT_STEP and
	SIMD_CLONE_ARG_TYPE_LINEAR_UVAL_CONSTANT_STEP cases explicitly.

	* semantics.c (finish_omp_clauses) <case OMP_CLAUSE_LINEAR>:
	For OMP_CLAUSE_LINEAR_REF don't require type to be
	integral or pointer.

	* g++.dg/vect/simd-clone-6.cc: New test.
	* g++.dg/gomp/declare-simd-6.C: New test.

From-SVN: r236648