Add a version annotation for the Q and q format codes.

Doc/lib/libstruct.tex

@@ -72,8 +72,9 @@ Notes:
 \item[(1)]
   The \character{q} and \character{Q} conversion codes are available in
   native mode only if the platform C compiler supports C \ctype{long long},
-  or, on Windows, \ctype{__int64}.  They're always available in standard
+  or, on Windows, \ctype{__int64}.  They are always available in standard
   modes.
+  \versionadded{2.2}
 \end{description}