Define RNA_STACK_ARRAY (usable everywhere in RNA), and make PYRNA_STACK_ARRAY use it.

source/blender/python/intern/bpy_props.h

@@ -34,6 +34,6 @@ PyObject *BPy_PointerProperty(PyObject *self, PyObject *args, PyObject *kw);
 PyObject *BPy_CollectionProperty(PyObject *self, PyObject *args, PyObject *kw);
 StructRNA *pointer_type_from_py(PyObject *value, const char *error_prefix);
 
-#define PYRNA_STACK_ARRAY 32
+#define PYRNA_STACK_ARRAY RNA_STACK_ARRAY
 
 #endif