Conflicts:
libs/gst/base/gstbasetransform.c
libs/gst/controller/gstinterpolationcontrolsource.c
libs/gst/controller/gstlfocontrolsource.c
plugins/elements/gstfilesrc.c
Dit not merge controller or basetransform changes.
This handles muxing of sparse/subtitle streams and has
lots of cleanup. Still missing is special support for
live streams but this can be added later without breaking
API/ABI.
Based on the version from the videomixer plugin.
https://bugzilla.gnome.org/show_bug.cgi?id=415754