Close an improperly-closed verbatim environment.

This closes SF patch #496215.

Add a little more detail to the example that had not been closed.

Doc/api/abstract.tex

@@ -860,6 +860,9 @@ PyObject *item;
 
 while (item = PyIter_Next(iter)) {
     /* do something with item */
+    ...
+    /* release reference when done */
+    Py_DECREF(item);
 }
 if (PyErr_Occurred()) {
     /* propogate error */
@@ -867,6 +870,8 @@ if (PyErr_Occurred()) {
 else {
     /* continue doing useful work */
 }
+\end{verbatim}
+
 
 \section{Buffer Protocol \label{abstract-buffer}}
 
@@ -897,7 +902,7 @@ else {
   Returns \code{1} if \var{o} supports the single-segment readable
   buffer interface.  Otherwise returns \code{0}.
   \versionadded{2.2}
-\enc{cfuncdesc}
+\end{cfuncdesc}
 
 \begin{cfuncdesc}{int}{PyObject_AsWriteBuffer}{PyObject *obj,
                                                const char **buffer,
@@ -909,5 +914,3 @@ else {
   \code{0} and sets a \exception{TypeError} on error.
   \versionadded{1.6}
 \end{cfuncdesc}
-
-\end{verbatim}