Add support for the following attributes in layout.conf to allow more
precise configuration of inheritance of settings from repositories:
  eclass-masters
  package.mask-masters
  use.aliases-masters
  use.force-masters
  use.mask-masters
Enable BytesWarnings.
Rename portage._sync_disabled_warnings to portage._sync_mode.
Deprecate portage.dbapi.porttree.portdbapi.porttree_root and portage.dbapi.porttree.portdbapi.eclassdb.
portage.eclass_cache.cache.__init__(): Deprecate overlays parameter.
(This parameter has been unused in Portage since commit 2bd2620142d15344f32ef67896c4fa88e5386953.)