gccrs: Fix ForeverStack::find_starting_point output parameter

gccrs: Fix ForeverStack::find_starting_point output parameter

gcc/rust/ChangeLog:

	* resolve/rust-forever-stack.h
	(ForeverStack::find_starting_point): Use type
	'std::reference_wrapper<Node> &' instead of 'Node &' for
	parameter starting_point.
	* resolve/rust-forever-stack.hxx
	(ForeverStack::find_starting_point): Likewise.
	(ForeverStack::resolve_path): Handle change to
	ForeverStack::find_starting_point.

Signed-off-by: Owen Avery <powerboat9.gamer@gmail.com>