rust_debug: Cast size_t values to unsigned long before printing.

rust_debug: Cast size_t values to unsigned long before printing.

Using %lu to format size_t values breaks 32 bit targets, and %zu is not
supported by one of the hosts GCC aims to support - HPUX

gcc/rust/ChangeLog:

	* backend/rust-compile-base.cc (HIRCompileBase::resolve_method_address):
	Cast size_t value to unsigned long.
	* expand/rust-proc-macro.cc (load_macros): Likewise.
	* typecheck/rust-hir-type-check-expr.cc (TypeCheckExpr::visit): Likewise.