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/space_buttons/buttons_texture.c b/source/blender/editors/space_buttons/buttons_texture.c
index 87ea011e0a7..03c8fbb4e66 100644
--- a/source/blender/editors/space_buttons/buttons_texture.c
+++ b/source/blender/editors/space_buttons/buttons_texture.c
@@ -385,7 +385,7 @@ static void template_texture_select(bContext *C, void *user_p, void *UNUSED(arg)
     if (user->ptr.type == &RNA_ParticleSettingsTextureSlot) {
       /* stupid exception for particle systems which still uses influence
        * from the old texture system, set the active texture slots as well */
-      ParticleSettings *part = user->ptr.id.data;
+      ParticleSettings *part = (ParticleSettings *)user->ptr.owner_id;
       int a;
 
       for (a = 0; a < MAX_MTEX; a++) {