Make CyObject struct appear earlier than type definitions

Cython/Utility/ModuleSetupCode.c

@@ -1545,3 +1545,7 @@ static void __Pyx_FastGilFuncInit(void) {
     CyObject_ATOMIC_REFCOUNT_TYPE ob_refcnt;                  \
     void (*cdealloc)(void* self);
 
+struct CyObject {
+  CyObject_HEAD
+};
+

Cython/Utility/ObjectHandling.c

@@ -1600,10 +1600,6 @@ try_unpack:
 //    int ob_refcnt;               \
 //    void (*cdealloc)(void * self);
 
-struct CyObject {
-  CyObject_HEAD
-};
-
 /* Cast argument to PyObject* type. */
 #define _CyObject_CAST(op) ((struct CyObject*)(op))