libvlc: add stream API
This is a follow-up of a very old patch-set: https://mailman.videolan.org/pipermail/vlc-devel/2016-May/107867.html
@Courmisch did a review:
Except it is essentially impossible because it requires use of VLC internals that are not exposed and should not be.
And this is out of scope anyhow. LibVLC is not a file system abstraction.
I fixed the 1st point.
I disagree with the second one. This feature is asked very regularly by LibVLC users, I hope it can be approved now.