libva: allow pre-releases.
libva: allow pre-releases.

Signed-off-by: Gwenole Beauchesne <729713629d9640cc095f1c77c692e1881f8093c4@intel.com>

halleyzhao/libva-fdo,01org/iotg-lin-gfx-libva,01org/iotg-lin-gfx-libva,android-ia/hardware_intel_libva,CyanogenMod/android_hardware_intel_libva,gbeauchesne/libva,zzhhui/libva,CyanogenMod/android_hardware_intel_libva,01org/iotg-lin-gfx-libva,zzhhui/libva,Distrotech/libva,Distrotech/libva,pma1/libva,pma1/libva,android-ia/hardware_intel_libva,gbeauchesne/libva,halleyzhao/libva-fdo,android-ia/hardware_intel_libva,chenxianqin/vaapi-libva,zzhhui/libva,CyanogenMod/android_hardware_intel_libva,01org/libva-cros,01org/libva-cros,01org/libva-cros,Distrotech/libva,chenxianqin/vaapi-libva,chenxianqin/vaapi-libva,halleyzhao/libva-fdo,pma1/libva,gbeauchesne/libva