The following implementation details where exposed as public symbols:
- _ges_container_get_priority_offset
- _ges_container_set_height
- _ges_container_set_priority_offset
- _ges_uri_asset_cleanup
but it was not correct and that should never have been used outside
GES.
Moving those declarations to the internal header and marking as
internal.
With the addition of the .def file for libges we need to make
sure the check-export script from common gets executed so that the
.def stays up to date.
https://bugzilla.gnome.org/show_bug.cgi?id=774641
