Move the GST_CXXFLAGS and GST_CFLAGS to the start of the includes set
to pull in the local gst-libs from there first, instead of listing
it explicitly.
Add some guards and fat warnings to the header files with still unstable
API, so people who just look at the installed headers know that it
actually is unstable API.
Also move schroedinger plugin. This creates a new library,
gstbasevideo-0.10, which will probably be merged back into
gstvideo-0.10 when this is moved back to -base.
