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, 2 insertions, 2 deletions

diff --git a/source/blender/makesrna/intern/rna_collection.c b/source/blender/makesrna/intern/rna_collection.c
index 15d73aae0ae..fb366422f34 100644
--- a/source/blender/makesrna/intern/rna_collection.c
+++ b/source/blender/makesrna/intern/rna_collection.c
@@ -134,7 +134,7 @@ static bool rna_Collection_objects_override_apply(Main *bmain,
              "Unsupported RNA override operation on collections' objects");
   UNUSED_VARS_NDEBUG(opop);
 
-  Collection *coll_dst = ptr_dst->id.data;
+  Collection *coll_dst = (Collection *)ptr_dst->owner_id;
 
   if (ptr_item_dst->type == NULL || ptr_item_src->type == NULL) {
     BLI_assert(0 && "invalid source or destination object.");
@@ -237,7 +237,7 @@ static bool rna_Collection_children_override_apply(Main *bmain,
              "Unsupported RNA override operation on collections' children");
   UNUSED_VARS_NDEBUG(opop);
 
-  Collection *coll_dst = ptr_dst->id.data;
+  Collection *coll_dst = (Collection *)ptr_dst->owner_id;
 
   if (ptr_item_dst->type == NULL || ptr_item_src->type == NULL) {
     BLI_assert(0 && "invalid source or destination sub-collection.");