MPEG-4 Audio Lossless Coding (ALS) encoder implementation

The project aims at enhancing and merging the MPEG-4 ALS encoder, which has been written already, into the official FFmpeg codebase. Second, the encoder is to be brought through the usual reviewing process to hit the codebase at the end of the timeline. Also, support for decoding 32-bit floating point data will be added to the decoder.