Added an example of iteration with for with a vector.

docs/src/userguide/wrapping_CPlusPlus.rst

@@ -463,11 +463,13 @@ For example::
     from libcpp.vector cimport vector
 
     cdef vector[int] vect
-    cdef int i
+    cdef int i, x
     for i in range(10):
         vect.push_back(i)
     for i in range(10):
         print(vect[i])
+    for x in vect:
+        print(x)
 
 The pxd files in ``/Cython/Includes/libcpp`` also work as good examples on
 how to declare C++ classes.