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/editors/interface/interface_eyedropper_datablock.c b/source/blender/editors/interface/interface_eyedropper_datablock.c
index efbe5922aa5..336fae45895 100644
--- a/source/blender/editors/interface/interface_eyedropper_datablock.c
+++ b/source/blender/editors/interface/interface_eyedropper_datablock.c
@@ -118,7 +118,7 @@ static int datadropper_init(bContext *C, wmOperator *op)
   ddr->idcode_name = TIP_(BKE_idcode_to_name(ddr->idcode));
 
   PointerRNA ptr = RNA_property_pointer_get(&ddr->ptr, ddr->prop);
-  ddr->init_id = ptr.id.data;
+  ddr->init_id = ptr.owner_id;
 
   return true;
 }
@@ -222,7 +222,7 @@ static bool datadropper_id_set(bContext *C, DataDropper *ddr, ID *id)
 
   ptr_value = RNA_property_pointer_get(&ddr->ptr, ddr->prop);
 
-  return (ptr_value.id.data == id);
+  return (ptr_value.owner_id == id);
 }
 
 /* single point sample & set */