Add VA_STATUS_ERROR_UNIMPLEMENTATION string representation.
Add VA_STATUS_ERROR_UNIMPLEMENTATION string representation.

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