address variaty of compiler warnings and code documentation

src/core1/done/audio/n_reverb.c

@@ -372,4 +372,4 @@ Acmd *__n_filterBuffer(ALLowPass *lp, s32 buff, Acmd *p)
     lp->first = 0;
 
     return ptr;
-}
+}

src/core1/done/audio/n_synsetvol.c

@@ -27,4 +27,4 @@ void n_alSynSetVol( N_ALVoice *v, s16 volume, ALMicroTime t)
         //(*f->setParam)(f, AL_FILTER_ADD_UPDATE, update);
          n_alEnvmixerParam(v->pvoice, AL_FILTER_ADD_UPDATE, update);       
     }
-}
+}

src/core1/done/gu/cosf.c

@@ -134,4 +134,4 @@ int	ix, xpt;
 	/* just give up and return 0.0 */
 
 	return ( zero.f );
-}
+}