* Fix for Icons and comboboxes mismatch in arpeggiator in Instrument Editor #5494
(https://github.com/LMMS/lmms/issues/5494)
Introduce a static const int variable for the default height of a ComboBox.
Set this height already in the constructor of the ComboBox object.
Update all modules setting the height of a ComboBox object to make use of the new constant.
* Replace 'const int' by 'constexpr int' after review.
* advanced config: expose hidden constants to user screen
* advanced config: add support for FFT window overlapping
* waterfall: display at native resolution on high-DPI screens
* waterfall: add cursor and improve label density
* FFT: fix normalization so that 0 dBFS matches full-scale sinewave
* FFT: decouple data acquisition from processing and display
* FFT: separate lock for reallocation (to avoid some needless waiting)
* moved ranges and other constants to a separate file
* debug: better performance measurements
* minor fixes
* build the ringbuffer library as part of LMMS core
