GCC has some optimization for the inclusion guard, but they only work if
the check is the outermost one.
We're fairly inconsistent because of historical reasons, so we should
ensure that we follow the same pattern in every public header.
Bug 882 - Allow child properties for containers implementing the
ClutterContainer interface (Øyvind Kolås)
* clutter/clutter-child-meta.[ch]: Base class for the metadata
of a ClutterActor inside a ClutterContainer; the ChildMeta
object implements a wrapper for storing data that is attached
to a ClutterActor only when it's part of a ClutterContainer.
The ChildMeta object is used to store the child properties
accessible through the ClutterContainer API.
* clutter/clutter-container.[ch]: Creates the ChildMeta for
each actor, in case the Container specifies the ChildMeta
type to use.
* clutter/Makefile.am: Add clutter-child-meta.[ch] to the build.
* clutter/clutter-marshal.list: Add the marshaller for the
ClutterContainer::child-notify signal.
* clutter/clutter-types.h: Declare ClutterContainer and
ClutterChildMeta to avoid recursive inclusion.
