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/gpencil/gpencil_data.c b/source/blender/editors/gpencil/gpencil_data.c
index 696c98c6646..e4d6a3e983d 100644
--- a/source/blender/editors/gpencil/gpencil_data.c
+++ b/source/blender/editors/gpencil/gpencil_data.c
@@ -105,7 +105,7 @@ static bool gp_data_add_poll(bContext *C)
 /* add new datablock - wrapper around API */
 static int gp_data_add_exec(bContext *C, wmOperator *op)
 {
-  PointerRNA gpd_owner = {{NULL}};
+  PointerRNA gpd_owner = {NULL};
   bGPdata **gpd_ptr = ED_gpencil_data_get_pointers(C, &gpd_owner);
   bool is_annotation = ED_gpencil_data_owner_is_annotation(&gpd_owner);
 
@@ -231,7 +231,7 @@ void GPENCIL_OT_data_unlink(wmOperatorType *ot)
 /* add new layer - wrapper around API */
 static int gp_layer_add_exec(bContext *C, wmOperator *op)
 {
-  PointerRNA gpd_owner = {{NULL}};
+  PointerRNA gpd_owner = {NULL};
   bGPdata **gpd_ptr = ED_gpencil_data_get_pointers(C, &gpd_owner);
   bool is_annotation = ED_gpencil_data_owner_is_annotation(&gpd_owner);