Moved an example of the language basics into the examples directory.

docs/examples/userguide/language_basics/cdef_block.pyx

+from __future__ import print_function
+
+cdef:
+    struct Spam:
+        int tons
+
+    int i
+    float a
+    Spam *p
+
+    void f(Spam *s):
+        print(s.tons, "Tons of spam")

docs/src/userguide/language_basics.rst

@@ -179,20 +179,9 @@ Grouping multiple C declarations
 --------------------------------
 
 If you have a series of declarations that all begin with :keyword:`cdef`, you
-can group them into a :keyword:`cdef` block like this::
+can group them into a :keyword:`cdef` block like this:
 
-    from __future__ import print_function
-
-    cdef:
-        struct Spam:
-            int tons
-
-        int i
-        float a
-        Spam *p
-
-        void f(Spam *s):
-            print(s.tons, "Tons of spam")
+.. literalinclude:: ../../examples/userguide/language_basics/cdef_block.pyx
 
 .. _cpdef:
 .. _cdef: