Log Message:
fluidsynth: update to 2.2.6.

Undeprecation and minor revisal of the OSS driver (#1038)
Minor improvements to CoreAudio and CoreMidi drivers (#1047, thanks to @bradhowes)
Fix sustained voices being held after ALL_CTRL_OFF (#1049)
Fix clobbering of PORTAMENTO_CTRL after ALL_CRTL_OFF (#1050)
Prevent Modulation Envelope from being stuck in decay phase, causing
detuned voices and potentially other audible glitches for some
soundfonts (#1059)
Fix a compilation issue with recent glib (#1063, thanks to @devingryu)