fft: add missing const.

This table was the largest object in FFmpeg's .data,
and really should be in .rodata.
Signed-off-by: Reimar Döffinger <Reimar.Doeffinger@gmx.de>

libavcodec/fft_init_table.c

@@ -53,7 +53,7 @@
  */
 #include "libavcodec/fft_table.h"
 
-int32_t w_tab_sr[MAX_FFT_SIZE/(4*16)] = {
+const int32_t w_tab_sr[MAX_FFT_SIZE/(4*16)] = {
     2147483647, 2147481121, 2147473542, 2147460908, 2147443222, 2147420483, 2147392690, 2147359845,
     2147321946, 2147278995, 2147230991, 2147177934, 2147119825, 2147056664, 2146988450, 2146915184,
     2146836866, 2146753497, 2146665076, 2146571603, 2146473080, 2146369505, 2146260881, 2146147205,

libavcodec/fft_table.h

@@ -59,7 +59,7 @@
 #define MAX_LOG2_NFFT 16 //!< Specifies maximum allowed fft size
 #define MAX_FFT_SIZE (1 << MAX_LOG2_NFFT)
 
-extern int32_t w_tab_sr[];
+extern const int32_t w_tab_sr[];
 extern uint16_t fft_offsets_lut[];
 void ff_fft_lut_init(uint16_t *table, int off, int size, int *index);
 

libavcodec/fft_template.c

@@ -229,7 +229,7 @@ static void fft_calc_c(FFTContext *s, FFTComplex *z) {
     FFTSample tmp1, tmp2, tmp3, tmp4, tmp5, tmp6, tmp7, tmp8;
     FFTComplex *tmpz;
     FFTSample w_re, w_im;
-    FFTSample *w_re_ptr, *w_im_ptr;
+    const FFTSample *w_re_ptr, *w_im_ptr;
     const int fft_size = (1 << s->nbits);
     int64_t accu;