RNA: Cleanup PointerRNA struct

The old layout of `PointerRNA` was confusing for historic reasons:
```
typedef struct PointerRNA {
  struct {
    void *data;
  } id;

  struct StructRNA *type;
  void *data;
} PointerRNA;
```

This patch updates it to:
```
typedef struct PointerRNA {
  struct ID *owner_id;
  struct StructRNA *type;
  void *data;
} PointerRNA;
```

Throughout the code base `id.data` was replaced with `owner_id`.
Furthermore, many explicit pointer type casts were added which
were implicit before. Some type casts to `ID *` were removed.

Reviewers: brecht, campbellbarton

Differential Revision: https://developer.blender.org/D5558

1 files changed, 1 insertions, 1 deletions

diff --git a/source/blender/editors/screen/screen_context.c b/source/blender/editors/screen/screen_context.c
index 2eb7f732534..6f8b25f782b 100644
--- a/source/blender/editors/screen/screen_context.c
+++ b/source/blender/editors/screen/screen_context.c
@@ -533,7 +533,7 @@ int ed_screen_context(const bContext *C, const char *member, bContextDataResult
     gpd_ptr = ED_gpencil_data_get_pointers_direct((ID *)sc, sa, scene, obact, &ptr);
 
     if (gpd_ptr) {
-      CTX_data_pointer_set(result, ptr.id.data, ptr.type, ptr.data);
+      CTX_data_pointer_set(result, ptr.owner_id, ptr.type, ptr.data);
       return 1;
     }
   }