gstreamer1 default backend package

[Thomas Klausner <wiz%NetBSD.org@localhost>]

Hi!

I've just added the package meta-pkgs/gstreamer1-default-backend; its
purpose is to install the gstreamer1 backend that's most suited to
your operating system, so that other packages that use gstreamer1 can
depend on it to make sure the user will hear something.

I've added defaults for Linux and NetBSD, but they are implemented as
options, so you can choose differently if you want.

Please add defaults for other operating systems (or change the
existing ones if you think one is better suited) and use it in your
gstreamer1 packages.

Thanks,
 Thomas