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

2 files changed, 2 insertions, 2 deletions

diff --git a/source/blender/editors/space_image/image_buttons.c b/source/blender/editors/space_image/image_buttons.c
index f1a29a1542d..64e1c02590e 100644
--- a/source/blender/editors/space_image/image_buttons.c
+++ b/source/blender/editors/space_image/image_buttons.c
@@ -991,7 +991,7 @@ void uiTemplateImage(uiLayout *layout,
 void uiTemplateImageSettings(uiLayout *layout, PointerRNA *imfptr, bool color_management)
 {
   ImageFormatData *imf = imfptr->data;
-  ID *id = imfptr->id.data;
+  ID *id = imfptr->owner_id;
   PointerRNA display_settings_ptr;
   PropertyRNA *prop;
   const int depth_ok = BKE_imtype_valid_depths(imf->imtype);
diff --git a/source/blender/editors/space_image/image_ops.c b/source/blender/editors/space_image/image_ops.c
index 05ba82b8bde..7ea693f2fd2 100644
--- a/source/blender/editors/space_image/image_ops.c
+++ b/source/blender/editors/space_image/image_ops.c
@@ -1431,7 +1431,7 @@ static int image_open_invoke(bContext *C, wmOperator *op, const wmEvent *UNUSED(
       Image *oldima;
 
       oldptr = RNA_property_pointer_get(&ptr, prop);
-      oldima = (Image *)oldptr.id.data;
+      oldima = (Image *)oldptr.owner_id;
       /* unlikely to fail but better avoid strange crash */
       if (oldima && GS(oldima->id.name) == ID_IM) {
         ima = oldima;