borrowck: BIR: scope handling

borrowck: BIR: scope handling

gcc/rust/ChangeLog:

	* checks/errors/borrowck/rust-bir-builder-expr-stmt.cc (ExprStmtBuilder::setup_loop):
	Loop handling.
	(ExprStmtBuilder::visit): Handle scopes.
	* checks/errors/borrowck/rust-bir-builder-internal.h (struct BuilderContext):
	Handle scopes.
	* checks/errors/borrowck/rust-bir-dump.cc (Dump::go): Dump scopes.
	(Dump::visit): Add scopes dump.
	(Dump::indent): Add indentation logic.
	(Dump::visit_scope): Dump scope.
	* checks/errors/borrowck/rust-bir-dump.h: Dump methods.
	* checks/errors/borrowck/rust-bir-place.h (std::numeric_limits::max): Scope constants.
	(struct Scope): Scope representation.
	(class PlaceDB): Scope tracking.

Signed-off-by: Jakub Dupak <dev@jakubdupak.com>