`rational_interval` printing gone wrong

[Ovascos]

Due to a missing #include <iostream>, the following code calls constructor Variable(const char*) and thus generates variables named "[ ", " ; ", " ]", "( ", " )", and " ; " in the default context at lines 73, 75, 77, 79, 81, and 83 (but at least printing works as expected).

libpoly/src/polyxx/rational_interval.cpp

Lines 70 to 85 in 7290c4b

	std::ostream& operator<<(std::ostream& os, const RationalInterval& i) {
	if (i.get_internal()->is_point) {
	assert(!i.get_internal()->a_open && !i.get_internal()->b_open);
	os << "[ ";
	stream_ptr(os, lp_rational_to_string(&(i.get_internal()->a)));
	os << " ; ";
	stream_ptr(os, lp_rational_to_string(&(i.get_internal()->a)));
	return os << " ]";
	}
	os << (i.get_internal()->a_open ? "( " : "[ ");
	stream_ptr(os, lp_rational_to_string(&(i.get_internal()->a)));
	os << " ; ";
	stream_ptr(os, lp_rational_to_string(&(i.get_internal()->b)));
	os << (i.get_internal()->b_open ? " )" : " ]");
	return os;
	}