btrfs-tree: add support for inode flags

Signed-off-by: Zygo Blaxell <bees@furryterror.org>

include/crucible/btrfs-tree.h

@@ -49,6 +49,7 @@ namespace crucible {
 		/// @}
 
 		/// @{ Inode items
+		uint64_t inode_flags() const;
 		uint64_t inode_size() const;
 		/// @}