gccrs: Improve Rib::Definition shadowing

gccrs: Improve Rib::Definition shadowing

gcc/rust/ChangeLog:

	* resolve/rust-finalize-imports-2.0.cc
	(GlobbingVisitor::visit): Replace calls to insert_shadowable with
	insert_globbed.
	* resolve/rust-forever-stack.h
	(ForeverStack::insert_globbed): Add.
	* resolve/rust-forever-stack.hxx
	(ForeverStack::insert_globbed): Add.
	(ForeverStack::dfs): Handle modifications to Rib::Definition
	fields.
	* resolve/rust-late-name-resolver-2.0.cc
	(Late::visit): Make IdentifierPattern-based declarations
	shadowable.
	* resolve/rust-name-resolution-context.cc
	(NameResolutionContext::insert_globbed): Add.
	* resolve/rust-name-resolution-context.h
	(NameResolutionContext::insert_globbed): Add.
	* resolve/rust-rib.cc
	(Rib::Definition::Definition): Use Rib::Definition::Mode to
	indicate shadowing mode instead of boolean, handle modifications
	to Rib::Definition fields.
	(Rib::Definition::is_ambiguous): Handle modifications to
	Rib::Definition fields.
	(Rib::Definition::to_string): Likewise.
	(Rib::Definition::Shadowable): Handle changed constructor
	signature.
	(Rib::Definition::NonShadowable): Likewise.
	(Rib::Definition::Globbed): Add.
	(Rib::insert): Handle changes to Rib::Definition fields.
	* resolve/rust-rib.h
	(Rib::Definition::Globbed): Add.
	(Rib::Definition::ids): Remove.
	(Rib::Definition::ids_shadowable): Add.
	(Rib::Definition::ids_non_shadowable): Add.
	(Rib::Definition::ids_globbed): Add.
	(Rib::Definition::get_node_id): Handle modifications to
	Rib::Definition fields.
	(Rib::Definition::Mode): Add.
	(Rib::Definition::Definition): Use Rib::Definition::Mode to
	indicate shadowing mode instead of boolean.

gcc/testsuite/ChangeLog:

	* rust/compile/nr2/exclude: Remove shadow1.rs.

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