Log Message:
fluidsynth: update to 2.3.7.

Fix SF3 decoder producing crackling sound for loud samples (#1380)
MIDI Format 2 is now rejected correctly since it was never supported (#1366)
Fix UTF8 encoding issues on Windows (#1388, thanks to @stardusteyes)
Fix a regression introduced in 2.3.2 causing fluidsynth to fail discovering Oboe \ 
(#1393)
Other minor bugs (#1291, #1403)