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_vfont.c b/source/blender/makesrna/intern/rna_vfont.c
index cf61fe07c68..3e96b5816e5 100644
--- a/source/blender/makesrna/intern/rna_vfont.c
+++ b/source/blender/makesrna/intern/rna_vfont.c
@@ -40,7 +40,7 @@
 /* matching fnction in rna_ID.c */
 static int rna_VectorFont_filepath_editable(PointerRNA *ptr, const char **UNUSED(r_info))
 {
-  VFont *vfont = ptr->id.data;
+  VFont *vfont = (VFont *)ptr->owner_id;
   if (BKE_vfont_is_builtin(vfont)) {
     return 0;
   }
@@ -51,7 +51,7 @@ static void rna_VectorFont_reload_update(Main *UNUSED(bmain),
                                          Scene *UNUSED(scene),
                                          PointerRNA *ptr)
 {
-  VFont *vf = ptr->id.data;
+  VFont *vf = (VFont *)ptr->owner_id;
   BKE_vfont_free_data(vf);
 
   /* update */