The colorspace conversion happens during the upload so the necessary hints
must be provided to ensure that the conversion works correctly.
At least the Mesa Intel driver will create a texture without error but
produces an incorrect result. Use eglQueryDmaBufModifiersEXT() to check if
non-external upload is supported for the given format.
Based on a patch from Carlos Rafael Giani <dv@pseudoterminal.org>.
https://bugzilla.gnome.org/show_bug.cgi?id=783521
We need different export decorators for the different libs.
For now no actual change though, just rename before the release,
and add prelude headers to define the new decorator to GST_EXPORT.
