Remove create_lcssa_for_virtual_phi and uses

The following expands the comment in vect_do_peeling as to why we
do not need create_lcssa_for_virtual_phi and removes that function.

That's the last bit I have queued for the vectorizer virtual LCSSA
cleanup.

	* tree-vect-loop-manip.cc (create_lcssa_for_virtual_phi):
	Remove.
	(vect_do_peeling): Do not call it, adjust comment.