Outliner: Refactor outliner tree-hash interfaces with C++

- Turn storage into an object with "automatic" memory management (RAII)
  so freeing is implicit and reliable.
- Turn functions into member functions, to have the data and its
  functions close together with controlled access that increases
  encapsulation and hiding implementation details.
- Use references to indicate null is not an expected value.
- Related minor cleanup (comments, use const etc.)

Couldn't spot any changes in performance.

1 files changed, 2 insertions, 2 deletions

diff --git a/source/blender/makesdna/DNA_space_types.h b/source/blender/makesdna/DNA_space_types.h
index 09446536657..75f2f6702e5 100644
--- a/source/blender/makesdna/DNA_space_types.h
+++ b/source/blender/makesdna/DNA_space_types.h
@@ -405,8 +405,8 @@ typedef enum eSpaceOutliner_StoreFlag {
   /* cleanup tree */
   SO_TREESTORE_CLEANUP = (1 << 0),
   SO_TREESTORE_UNUSED_1 = (1 << 1), /* cleared */
-  /* rebuild the tree, similar to cleanup,
-   * but defer a call to BKE_outliner_treehash_rebuild_from_treestore instead */
+  /** Rebuild the tree, similar to cleanup, but defer a call to
+   * bke::outliner::treehash::rebuild_from_treestore instead. */
   SO_TREESTORE_REBUILD = (1 << 2),
 } eSpaceOutliner_StoreFlag;