Add new BRC encoder mode, Constant Rate Factor (CRF)
Add new BRC encoder mode, Constant Rate Factor (CRF)

In this mode the user provides a quality factor from 1-51
with 1 being the best quality.  The goal is to keep a
constant quality but will compress different areas by different
amounts taking motion into account.  Subjective quality will improve.

From penne.y.lee at intel.com

Signed-off-by: Austin Yuan <f447c34e4ebcef84a81b40a8d4dbc448a14e5570@intel.com>

halleyzhao/libva-fdo,halleyzhao/libva-fdo,halleyzhao/libva-fdo,android-ia/hardware_intel_libva,CyanogenMod/android_hardware_intel_libva,android-ia/hardware_intel_libva,CyanogenMod/android_hardware_intel_libva,android-ia/hardware_intel_libva,CyanogenMod/android_hardware_intel_libva