* Accept None as NULL pointers through python function calls.
* Added type callback for pointers back, it's useful still in
some cases. Made Object.data editable using this, the pointer
type varying based on object type.
* Wrap pin ID pointer in buttons space.
* Added subclasses for text and surface curve ID blocks, to
organize data better and get proper icons.
* Added RNA_type_to_ID_code and ID_code_to_RNA_type functions.
* Update RNA_access.h with new RNA types.