binding.rs generation with bindgen is optional.

By default, a pre-generated binding.rs is copied in OUT_DIR. This allows
for example to build on Windows and link against a standard VLC
installation.

Feature "use-bindgen" will trigger binding generation.

Improve linking on Windows

See merge request mfkl/vlc-rs!1

VLM support

* Refactored VLM methods into a VLM trait in it's own module
* Added more VLM methods

Update repository to Rust edition 2018

Signed-off-by: Aron Heinecke <aron.heinecke@t-online.de>

Implement Instance args