Method begin

src/utils/backward.hpp:573–578

		return Trace(_stacktrace[idx + skip_n_firsts()], idx);
	}
	void** begin() {
		if (size()) {
			return &_stacktrace[skip_n_firsts()];
		}
		return 0;
	}

protected:
	std::vector<void*> _stacktrace;