Merge branch 'ps/odb-cleanup'

Various code clean-up around odb subsystem. * ps/odb-cleanup: odb: drop unneeded headers and forward decls odb: rename `odb_has_object()` flags odb: use enum for `odb_write_object` flags odb: rename `odb_write_object()` flags treewide: use enum for `odb_for_each_object()` flags CodingGuidelines: document our style for flags