Remove some more DOS related stuff

Doxyfile

@@ -109,13 +109,10 @@ FILE_PATTERNS          = *.c \
                          *.mm \
                          *.dox
 RECURSIVE              = YES
-EXCLUDE                = ./src/djgppdos/internal.h \
-                         ./src/djgppdos/setup.c \
-                         ./src/sdl/IMG_xpm.c \
+EXCLUDE                = ./src/sdl/IMG_xpm.c \
                          ./src/sdl/SRB2DC/scramble.c
 EXCLUDE_SYMLINKS       = NO
 EXCLUDE_PATTERNS       = */src/hardware/*/* \
-                         */src/djgppdos/bcd.? \
                          */src/sdl/SDL_main/* \
                          */src/*/*_private.h \
                          */src/sdl/*/*help.? \

src/s_sound.c

@@ -2469,10 +2469,6 @@ void S_SetMusicVolume(INT32 digvolume, INT32 seqvolume)
 	CV_SetValue(&cv_midimusicvolume, seqvolume&31);
 	actualmidimusicvolume = cv_midimusicvolume.value;   //check for change of var
 
-#ifdef DJGPPDOS
-	digvolume = seqvolume = 31;
-#endif
-
 	switch(I_SongType())
 	{
 		case MU_MID: