update fluidsynth code

"Attached a new patch based on the work of truth5678 and Matt Giuca; it
removes the need for patching Fluidsynth's synth.h (though you may or
may not want to patch ipv6 with truth5678's patch if using code from
Fluidsynth's git) and gives the user control over most of Fluidsynth's
parameters using DosBox.conf (with its own parameters, not midiconf)."

http://www.vogons.org/viewtopic.php?f=32&t=27831&start=20#p385413

Signed-off-by: Ulrich Hecht <ulrich.hecht@gmail.com>
ide: dump std::min() to fix 64-bit build

Signed-off-by: Ulrich Hecht <ulrich.hecht@gmail.com>
sdlmain: fix mingw32 build

Signed-off-by: Ulrich Hecht <ulrich.hecht@gmail.com>