package/vlc: add support for ffmpeg 3.0

package/vlc: add support for ffmpeg 3.0

Instead of bumping vlc to git master (no vlc 3.x release yet) we use a
patch from deb-multimedia.org which provides the necessary changes for
ffmpeg 3.x support to vlc 2.2, compile-tested using this defconfig:

    BR2_TOOLCHAIN_BUILDROOT_WCHAR=y
    BR2_TOOLCHAIN_BUILDROOT_CXX=y
    BR2_PACKAGE_FFMPEG=y
    BR2_PACKAGE_FFMPEG_GPL=y
    BR2_PACKAGE_FFMPEG_POSTPROC=y
    BR2_PACKAGE_FFMPEG_SWSCALE=y
    BR2_PACKAGE_VLC=y

This patch can be removed when vlc is bumped to 3.x.

Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>