sdl12-compat: comment out drmp3_exp, drmp3_sin and drmp3_cos inlines and math.h header

From d4f99d4f19e42fbe1f205278f35e4ad5c95bf0d8 Mon Sep 17 00:00:00 2001
From: Ozkan Sezer <[EMAIL REDACTED]>
Date: Tue, 15 Jun 2021 23:20:02 +0300
Subject: [PATCH] comment out drmp3_exp, drmp3_sin and drmp3_cos inlines and
 math.h header

they aren't used.
---
 src/dr_mp3.h | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/src/dr_mp3.h b/src/dr_mp3.h
index 9e61bdf..b2e20f0 100644
--- a/src/dr_mp3.h
+++ b/src/dr_mp3.h
@@ -2389,7 +2389,9 @@ DRMP3_API void drmp3dec_f32_to_s16(const float *in, drmp3_int16 *out, size_t num
  Main Public API
 
  ************************************************************************************************************************************************************/
+#if 0 /* not used. */
 #include <math.h>   /* For sin() and exp(). */
+#endif
 
 #if defined(SIZE_MAX)
     #define DRMP3_SIZE_MAX  SIZE_MAX
@@ -2476,7 +2478,7 @@ static DRMP3_INLINE drmp3_uint32 drmp3_gcf_u32(drmp3_uint32 a, drmp3_uint32 b)
     return a;
 }
 
-
+#if 0 /* not used. */
 static DRMP3_INLINE double drmp3_sin(double x)
 {
     /* TODO: Implement custom sin(x). */
@@ -2493,7 +2495,7 @@ static DRMP3_INLINE double drmp3_cos(double x)
 {
     return drmp3_sin((DRMP3_PI_D*0.5) - x);
 }
-
+#endif
 
 static void* drmp3__malloc_default(size_t sz, void* pUserData)
 {