(1) to be multithreaded,
(2) to work on multichannel audio and
(3) to work on 48k and 44.1k audio.
Allow multiple impulse response (IR) files with a new setting: "convolution_ir_files"
When convolution starts, Shairport Sync will look for an IR file with a sample rate
matching the input (44.1k or 48k) and channel count.
If one can't be found, it will look for a single-channel IR file with the same rate.
It will always choose the first match in the file list supplied "convolution_ir_files".
Allow multithreading -- use the "convolution_thread_pool_size" to set the number of threads to use.
Deprecate "convolution" -- use "convolution_enabled" instead.
Deprecate "convolution_max_length" -- use "convolution_max_length_in_seconds" instead.
Deprecate "convolution_ir_file" -- use "convolution_ir_files" instead.
Update corresponding D-Bus methods and properties.
Update the loudness code to work on 48k and well as 44.1k audio and with multichannel audio.
Deprecate "loudness" -- use "loudness_enabled" instead.
Update corresponding D-Bus methods and properties.
Fix a deprecated FFmpeg warning.
Update HiFi-LoFi FFT convolver to latest available.
Mike Brady
d043f98330