Add support for SLP vectorization of OpenMP SIMD clone calls

Add support for SLP vectorization of OpenMP SIMD clone calls

This adds support for SLP vectorization of OpenMP SIMD clone calls.
There's a complication when vectorizing calls involving virtual
operands since this is now for the first time not only leafs (loads
or stores).  With SLP this runs into the issue that placement of
the vectorized stmts is not necessarily at one of the original
scalar stmts which leads to the magic updating virtual operands
in vect_finish_stmt_generation not working.  So we run into the
assert that updating virtual operands isn't necessary.  I've
papered over this similar to how we do for mismatched const/pure
attribution by setting vinfo->any_known_not_updated_vssa.

I've added two basic testcases with multi-lane SLP and verified
that with single-lane SLP enabled the rest of the existing testcases
pass.

	* tree-vect-slp.cc (mask_call_maps): New.
	(vect_get_operand_map): Handle IFN_MASK_CALL.
	(vect_build_slp_tree_1): Likewise.
	* tree-vect-stmts.cc (vectorizable_simd_clone_call): Handle
	SLP.

	* gcc.dg/vect/slp-simd-clone-1.c: New testcase.
	* gcc.dg/vect/slp-simd-clone-2.c: Likewise.