Import a patch from the GCC mainline to fix an infinite recursion in the Rust demangler.

	PR 98886
	PR 99935
	* rust-demangle.c (struct rust_demangler): Add a recursion
	counter.
	(demangle_path): Increment/decrement the recursion counter upon
	entry and exit.  Fail if the counter exceeds a fixed limit.
	(demangle_type): Likewise.
	(rust_demangle_callback): Initialise the recursion counter,
	disabling if requested by the option flags.