New feature: 16 bit preload buffers to reduce the memory footprint by 50%

[Christoph Hart]

I just finished a rewrite of the streaming engine so that it uses 16bit preload buffers when using HLAC samples. By default, HISE (and almost every software written in JUCE), uses 32bit floating point data for internal buffers, however in case of preload buffers this creates a significant overhead, especially annoying on iOS devices with tight memory.

If you use .wav or .aiff files, then it will still use the 32bit float buffers. However for HLAC compressed samples, it switches to the 16bit buffer now (so another great reason to use HLAC)

This was a rather big rewrite, so it might be possible that there are some edge cases that I have overseen, in this case let me know then I'll fix it.