Fix more compilation warnings

src/audio/mint/SDL_mintaudio.c

@@ -144,7 +144,7 @@ int SDL_MintAudio_SearchFrequency(_THIS, int desired_freq)
 /* Check if FPU is present */
 void SDL_MintAudio_CheckFpu(void)
 {
-	unsigned long cookie_fpu;
+	long cookie_fpu;
 
 	SDL_MintAudio_hasfpu = 0;
 	if (Getcookie(C__FPU, &cookie_fpu) != C_FOUND) {

src/audio/mint/SDL_mintaudio_dma8.c

@@ -59,7 +59,7 @@
 
 /*--- Static variables ---*/
 
-static unsigned long cookie_snd, cookie_mch;
+static long cookie_snd, cookie_mch;
 
 /*--- Audio driver functions ---*/
 

src/audio/mint/SDL_mintaudio_gsxb.c

@@ -59,7 +59,7 @@
 
 /*--- Static variables ---*/
 
-static unsigned long cookie_snd, cookie_gsxb;
+static long cookie_snd, cookie_gsxb;
 
 /*--- Audio driver functions ---*/
 

src/audio/mint/SDL_mintaudio_mcsn.c

@@ -61,7 +61,7 @@
 
 /*--- Static variables ---*/
 
-static unsigned long cookie_snd, cookie_mch;
+static long cookie_snd, cookie_mch;
 static cookie_mcsn_t *cookie_mcsn;
 
 /*--- Audio driver functions ---*/
@@ -79,7 +79,7 @@ static void Mint_InitAudio(_THIS, SDL_AudioSpec *spec);
 
 static int Audio_Available(void)
 {
-	unsigned long dummy;
+	long dummy;
 	const char *envr = SDL_getenv("SDL_AUDIODRIVER");
 
 	SDL_MintAudio_mint_present = (Getcookie(C_MiNT, &dummy) == C_FOUND);