[intro.object] Say "member subobject" instead of "data member"

when talking about objects

Author: languagelawyer

source/basic.tex

@@ -3253,7 +3253,7 @@
 \end{itemize}
 
 \pnum
-If a complete object, a data member\iref{class.mem}, or an array element is of
+If a complete object, a member subobject, or an array element is of
 class type, its type is considered the \defn{most derived
 class}, to distinguish it from the class type of any base class subobject;
 an object of a most derived class type or of a non-class type is called a