Update dr_mp3.

extras/dr_mp3.h

 /*
 MP3 audio decoder. Choice of public domain or MIT-0. See license statements at the end of this file.
-dr_mp3 - v0.5.5 - 2020-01-29
+dr_mp3 - v0.5.6 - 2020-02-12
 
 David Reid - mackron@gmail.com
 
@@ -2137,7 +2137,7 @@ static int drmp3d_find_frame(const drmp3_uint8 *mp3, int mp3_bytes, int *free_fo
         }
     }
     *ptr_frame_bytes = 0;
-    return i;
+    return mp3_bytes;
 }
 
 void drmp3dec_init(drmp3dec *dec)
@@ -2242,8 +2242,6 @@ int drmp3dec_decode_frame(drmp3dec *dec, const unsigned char *mp3, int mp3_bytes
 
 void drmp3dec_f32_to_s16(const float *in, drmp3_int16 *out, int num_samples)
 {
-    if(num_samples > 0)
-    {
     int i = 0;
 #if DRMP3_HAVE_SIMD
     int aligned_count = num_samples & ~7;
@@ -2296,7 +2294,6 @@ void drmp3dec_f32_to_s16(const float *in, drmp3_int16 *out, int num_samples)
             out[i] = s;
         }
     }
-    }
 }
 
 
@@ -4010,6 +4007,9 @@ DIFFERENCES BETWEEN minimp3 AND dr_mp3
 /*
 REVISION HISTORY
 ================
+v0.5.6 - 2020-02-12
+  - Bring up to date with minimp3.
+
 v0.5.5 - 2020-01-29
   - Fix a memory allocation bug in high level s16 decoding APIs.