libstagefright: Add Utilities for QC Enhancements

Introduce a QCUtils file containing utility methods
for QC enhancements. Enable these features only if
TARGET_ENABLE_QC_AV_ENHANCEMENTS is true.
Add following enhancements:
 - High Frame Rate (HFR) recording
 - Shell property to disable audio
 - Shell property to override encoding profiles
 - Support for B frame encoding

Change-Id: I466e7c4923db3c4d7516fb02d34dad840a0d114e