fluidsynth 2.1.3

• fix a cross-compilation failure from Win32 to WinARM (#630)
• fix issues while fluid_player is seeking (#634, #646)
• fix a NULL pointer dereference if synth.dynamic-sample-loading is enabled (#635)
• fix a NULL pointer dereference in delete_rvoice_mixer_threads() (#640)
• fix a NULL pointer dereference in the soundfont loader (#647, thanks to @jjceresa)
• fix dsound driver playing garbage when terminating fluidsynth (#642, thanks to @jjceresa)
• avoid memory leaks when using libinstpatch (#643)