vaapi is not autoprobed

When loading VLC if the HW acceleration method is set to automatic it tries vdpau first then falls back to software methods immediately on failure without first attempting other hw acceleration options.

On my system VDPAU fails with the following (Checked 2.2.0 and 3.0.0 nightly ppa) (3.0.0!~~git20151221+r62900+34~ubuntu15.04.1)

Failed to open VDPAU backend libvdpau_i965.so: cannot open shared object file: No such file or directory

This a valid issue with the system directly in itself. VDPAU backend doesn't work well at all on my system (I installed the packages to try... slideshow time).

I did find though that VA-API via X11 or DRM works just fine.

libva info: VA-API version 0.37.0
libva info: va_getDriverName() returns 0
libva info: Trying to open /usr/lib/x86_64-linux-gnu/dri/i965_drv_video.so
libva info: Found init function __vaDriverInit_0_37
libva info: va_openDriver() returns 0
[00007f72e8de0d28] avcodec decoder: Using Intel i965 driver for Intel(R) Haswell Mobile - 1.5.0 for hardware decoding

It would be nice if VLC tried other available methods before giving up and going to software mode.