bugfixes:
- fix buffer overflow in audio buffer when calling reset_buffer (used in fifo input)
- cavacore: fix segfault when setting 0Hz lower cut off
- framerate <= 1 msec wait was multiplied by 1000 instead of divided
improvements:
- cavacore: don't print to stdout or call exit, use error status flag in cava_plan instead
- cavacore: add extern C construct for c++ compilers
- add license in cavacore header file
- remove build dependency on xxd, use incbin instead