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, 1 insertions, 1 deletions

diff --git a/source/blender/editors/curve/editfont.c b/source/blender/editors/curve/editfont.c
index f0c1abff201..9973c50c270 100644
--- a/source/blender/editors/curve/editfont.c
+++ b/source/blender/editors/curve/editfont.c
@@ -2031,7 +2031,7 @@ static int open_invoke(bContext *C, wmOperator *op, const wmEvent *UNUSED(event)
 
   if (pprop->prop) {
     idptr = RNA_property_pointer_get((PointerRNA *)pprop, pprop->prop);
-    vfont = idptr.id.data;
+    vfont = (VFont *)idptr.owner_id;
   }
 
   path = (vfont && !BKE_vfont_is_builtin(vfont)) ? vfont->name : U.fontdir;