default S bound(S s1, S s2) {
			if (s1.isEmpty()) {
				return s2;
			}
			if (s2.isEmpty()) {
				return s1;
			}
			return closed(min(s1.min(), s2.min()), max(s1.max(), s2.max()));
		}
Compute the smallest span which contains two spans

@param s1 a span
@param s2 another span
@return the bounding span
Ghidra/Framework/Emulation/src/main/java/generic/Span.java