Using Debian gir files

But kept the changes in commit 485d7e48 and 9265cc82

Using Debian gir files

Fixes https://github.com/sdroege/gstreamer-rs/pull/84

Only automatic bindings for now, which is enough to allow
implementing a simple rtsp-server example.

Depends on https://github.com/sdroege/gstreamer-sys/pull/8

Uses a new gir feature proposed at
https://github.com/gtk-rs/gir/pull/539 to make doc regeneration
easier.

Fixes https://github.com/sdroege/gstreamer-rs/pull/80

Should fix https://github.com/sdroege/gstreamer-rs/issues/68

Also fix structure ownership for the cache data API

Various nullability, types and usability fixes. The player configuration
is a new type now that can deref to a structure

This avoids depending on gst_flow_combiner_ref/unref which were
introduced in gstreamer-1.12.1.

Fixes https://github.com/sdroege/gstreamer-rs/pull/40

Fixes https://github.com/sdroege/gstreamer-rs/pull/36

And regenerate everything.

Requires
  https://github.com/gtk-rs/gir/pull/365
  https://github.com/gtk-rs/gir/pull/364
to be merged for autogeneration of the bindings.

Requires
  https://github.com/gtk-rs/gir/issues/367
for fixing memory leaks.