Added data history buffer, just alloc so far
To be used as secondary data argument for the .jl function:
Pass the current (small) buffer to ensure low latency, returning this buffer will leave data unchanged.
Also pass a longer, circular buffer that holds more data history.
This way it's easy to implement event detectors with minimal extra housekeeping.
julia function now works on current data buffer and performs in-place operations
adhere to julia in-place naming convention