-- errno.h is required for 'errno';
-- don't use str(n)casecmp and rely on ZDoom CMake handling;
-- add a missing parenthesis around a 'signed char' cast;
-- remove an unneeded GNU_SOURCE redefinition;
-- the non-MSVC side of snd_mididevice was not adapted to the new code, making wildmidi unavailable through the menu.