fix C compiler error: missing declarations if generators but not coroutines are used

Cython/Utility/Coroutine.c

@@ -399,6 +399,9 @@ static __pyx_CoroutineObject *__Pyx__Coroutine_NewInit(
             PyObject *name, PyObject *qualname, PyObject *module_name); /*proto*/
 
 static int __Pyx_Coroutine_clear(PyObject *self); /*proto*/
+static PyObject *__Pyx_Coroutine_Send(PyObject *self, PyObject *value); /*proto*/
+static PyObject *__Pyx_Coroutine_Close(PyObject *self); /*proto*/
+static PyObject *__Pyx_Coroutine_Throw(PyObject *gen, PyObject *args); /*proto*/
 
 #if 1 || PY_VERSION_HEX < 0x030300B0
 static int __Pyx_PyGen_FetchStopIterationValue(PyObject **pvalue); /*proto*/
@@ -419,9 +422,6 @@ static PyTypeObject *__pyx_CoroutineAwaitType = 0;
 
 static int __pyx_Coroutine_init(void); /*proto*/
 static PyObject *__Pyx__Coroutine_await(PyObject *coroutine); /*proto*/
-static PyObject *__Pyx_Coroutine_Send(PyObject *self, PyObject *value); /*proto*/
-static PyObject *__Pyx_Coroutine_Close(PyObject *self); /*proto*/
-static PyObject *__Pyx_Coroutine_Throw(PyObject *gen, PyObject *args); /*proto*/
 
 
 //////////////////// Generator.proto ////////////////////