swr: Mark src as const in swr_resample()

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

libswresample/resample2.c

@@ -250,7 +250,7 @@ void swr_compensate(struct SwrContext *s, int sample_delta, int compensation_dis
     c->dst_incr = c->ideal_dst_incr - c->ideal_dst_incr * (int64_t)sample_delta / compensation_distance;
 }
 
-int swr_resample(AVResampleContext *c, short *dst, short *src, int *consumed, int src_size, int dst_size, int update_ctx){
+int swr_resample(AVResampleContext *c, short *dst, const short *src, int *consumed, int src_size, int dst_size, int update_ctx){
     int dst_index, i;
     int index= c->index;
     int frac= c->frac;

libswresample/swresample_internal.h

@@ -72,7 +72,7 @@ struct AVResampleContext *swr_resample_init(struct AVResampleContext *, int out_
 void swr_resample_free(struct AVResampleContext **c);
 int swr_multiple_resample(struct AVResampleContext *c, AudioData *dst, int dst_size, AudioData *src, int src_size, int *consumed);
 void swr_resample_compensate(struct AVResampleContext *c, int sample_delta, int compensation_distance);
-int swr_resample(struct AVResampleContext *c, short *dst, short *src, int *consumed, int src_size, int dst_size, int update_ctx);
+int swr_resample(struct AVResampleContext *c, short *dst, const short *src, int *consumed, int src_size, int dst_size, int update_ctx);
 
 int swr_rematrix_init(SwrContext *s);
 int swr_rematrix(SwrContext *s, AudioData *out, AudioData *in, int len, int mustcopy);