MP3Extractor and MP3 decoder fixes - DO NOT MERGE

cherry-picked the following patches from HC branch:
o PV's mp3 decoder mistreated inputBufferCurrentLength in unit of bytes as in unit of bits
o Do not enforce the rule in MP3Extractor that all audio frames in an mp3 file must have the same mode
o When the temp buffer wraps around, the next read position should start
    from what have been read to avoid reading the same remaining bytes in
    the buffer again.
o Speed up MP3Extractor using cached reads

bug - 4083532

Change-Id: I7bbd2bd358fd5ee322287866cb8ee0c2bb217fea