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Fix #20

Also:
- use the same patterns as gstreamer-rs and gst-plugins-rs ci.
- remove unused cross build template
- update from Rust 1.36 to 1.40

Update minimum Rust version to 1.36, GStreamer to 1.16.1 and explicitly use Debian buster docker images

The ARM/Windows cross-builds were not too useful on their own and we
should rather set up proper CI for them.

Too many dependencies switched and we can't really keep everything at an
older version.

Commented out for now until stable becomes 1.32.

gstreamer-rtsp-server and gstreamer-editing-services are disabled for
now until there's a new release of them, or once we start building
against git master of them.

Fixes #16

All files are autogenerated and don't conform to what rustfmt would do

Similar to how ti was done for gstreamer-rs.
See [1] for more.

[1] https://github.com/sdroege/gstreamer-rs/pull/132