aac: add math.h needed for log2f()

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/aaccoder.c

@@ -31,6 +31,7 @@
  ***********************************/
 
 #include <float.h>
+#include <math.h>
 #include "avcodec.h"
 #include "put_bits.h"
 #include "aac.h"

libavcodec/aacsbr.c

@@ -35,6 +35,7 @@
 
 #include <stdint.h>
 #include <float.h>
+#include <math.h>
 
 #define ENVELOPE_ADJUSTMENT_OFFSET 2
 #define NOISE_FLOOR_OFFSET 6.0f