[yocto] Possible introspection failure in master

[alexander.kanavin at linux.intel.com]

> The gstreamer _git recipes have not been updated to include the
> gobject introspection patches which were applied to the 1.6.3 recipes.

Yeah, I forgot about the git recipes, as they're totally hidden from
default builds. I'll get them fixed.

> Try disabling gobject introspection via DISTRO or MACHINE features, ie:
>
>   MACHINE_FEATURES_BACKFILL_CONSIDERED_append = "
> gobject-introspection-data"

That is not going to help, I'm afraid. The recipes need further custom
fixing even when introspection is disabled.

Alex