Bug 1804058 FLAC extractor

Note: dependent on external/flac for libFLAC

Implemented and tested:
 * FLAC container
 * mono and stereo
 * standard sample rates
 * standard bit depths
 * sniffer
 * media scanner
 * Vorbis comment metadata including album art
 * random access seeking with "torture test"
 * web browser integration for audio/flac (not audio/x-flac), but
   note that most web servers don't correctly report the MIME type

Not implemented:
 * 24-bit to 16-bit dither or noise shaping in AudioFlinger
 * 96 kHz to 44.1 or 48 kHz downsampling low pass filter in AudioFlinger
 * replay gain is better done in AudioFlinger
 * multi-channel, would need AudioFlinger support
 * Ogg container, does not seem to be very popular yet

Change-Id: I300873e8c0cfc2e95403d9adb5064d16a2923f17
12 files changed