Fix unicode iteration in the limited C-API.

Cython/Utility/ModuleSetupCode.c

@@ -675,10 +675,11 @@ static CYTHON_INLINE PyObject * __Pyx_PyDict_GetItemStrWithError(PyObject *dict,
   #define __Pyx_PyUnicode_READY(op)       (0)
   #define __Pyx_PyUnicode_GET_LENGTH(u)   PyUnicode_GetLength(u)
   #define __Pyx_PyUnicode_READ_CHAR(u, i) PyUnicode_ReadChar(u, i)
-  #define __Pyx_PyUnicode_MAX_CHAR_VALUE(u)   (1114111)
-  //#define __Pyx_PyUnicode_KIND(u)             /* not available */
-  //#define __Pyx_PyUnicode_DATA(u)             /* not available */
-  //#define __Pyx_PyUnicode_READ(k, d, i)       /* not available */
+  #define __Pyx_PyUnicode_MAX_CHAR_VALUE(u)   ((void)u, 1114111)
+  #define __Pyx_PyUnicode_KIND(u)         ((void)u, (0))
+  // __Pyx_PyUnicode_DATA() and __Pyx_PyUnicode_READ() must go together, e.g. for iteration.
+  #define __Pyx_PyUnicode_DATA(u)         ((void*)u)
+  #define __Pyx_PyUnicode_READ(k, d, i)   ((void)k, PyUnicode_ReadChar((PyObject*)(d), i))
   //#define __Pyx_PyUnicode_WRITE(k, d, i, ch)  /* not available */
   #define __Pyx_PyUnicode_IS_TRUE(u)      (0 != PyUnicode_GetLength(u))
 #elif PY_VERSION_HEX > 0x03030000 && defined(PyUnicode_KIND)