Fixed a bunch of compile warnings on Mac OS X

--HG--
extra : convert_revision : svn%3Ac70aab31-4412-0410-b14c-859654838e24/trunk%403191

src/audio/SDL_audiocvt.c

@@ -1622,7 +1622,6 @@ int
 SDL_BuildWindowedSinc(SDL_AudioCVT * cvt, SDL_AudioFormat format,
                       unsigned int m)
 {
-    float fScale;               /* scale factor for fixed point */
     float *fSinc;               /* floating point sinc buffer, to be converted to fixed point */
     float fc;                   /* cutoff frequency */
     float two_pi_fc, two_pi_over_m, four_pi_over_m, m_over_two;
@@ -1708,6 +1707,8 @@ SDL_BuildWindowedSinc(SDL_AudioCVT * cvt, SDL_AudioFormat format,
     /* Clean up */
 #undef convert_fixed
     SDL_stack_free(fSinc);
+
+    return 0;
 }
 
 /* This is used to reduce the resampling ratio */

src/audio/macosx/SDL_coreaudio.c

@@ -418,7 +418,6 @@ prepare_audiounit(_THIS, const char *devname, int iscapture,
     AURenderCallbackStruct callback;
     ComponentDescription desc;
     Component comp = NULL;
-    int use_system_device = 0;
     UInt32 enableIO = 0;
     const AudioUnitElement output_bus = 0;
     const AudioUnitElement input_bus = 1;

src/audio/macrom/SDL_romaudio.c

@@ -89,6 +89,7 @@ mix_buffer(SDL_AudioDevice * audio, UInt8 * buffer)
     DecrementAtomic((SInt32 *) & need_to_mix);
 }
 
+#ifndef __MACOSX__
 static void
 SNDMGR_LockDevice(_THIS)
 {
@@ -114,6 +115,7 @@ SNDMGR_UnlockDevice(_THIS)
         mix_buffer(this, buffer[fill_me]);
     }
 }
+#endif // __MACOSX__
 
 static void
 callBackProc(SndChannel * chan, SndCommand * cmd_passed)