tree-optimization/108752 - vectorize emulated vectors in lowered form

tree-optimization/108752 - vectorize emulated vectors in lowered form

The following makes sure to emit operations lowered to bit operations
when vectorizing using emulated vectors.  This avoids relying on
the vector lowering pass adhering to the exact same cost considerations
as the vectorizer.

	PR tree-optimization/108752
	* tree-vect-generic.cc (build_replicated_const): Rename
	to build_replicated_int_cst and move to tree.{h,cc}.
	(do_plus_minus): Adjust.
	(do_negate): Likewise.
	* tree-vect-stmts.cc (vectorizable_operation): Emit emulated
	arithmetic vector operations in lowered form.
	* tree.h (build_replicated_int_cst): Declare.
	* tree.cc (build_replicated_int_cst): Moved from
	tree-vect-generic.cc build_replicated_const.