Patch #744238: Explain that different string types also may compare equal.

Doc/lib/libstdtypes.tex

@@ -144,7 +144,7 @@ Notes:
 
 \end{description}
 
-Objects of different types, except different numeric types, never
+Objects of different types, except different numeric types and different string types, never
 compare equal; such objects are ordered consistently but arbitrarily
 (so that sorting a heterogeneous array yields a consistent result).
 Furthermore, some types (for example, file objects) support only a