avcodec: add const qualifier to avcodec_find_best_pix_fmt2 args

avcodec_find_best_pix_fmt2 does not modify its first argument so may be
marked const.  This avoids a warning when passing in AVCodec.pix_fmts.
Signed-off-by: Dylan Simon <dylan@dylex.net>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/avcodec.h

@@ -4608,7 +4608,7 @@ enum AVPixelFormat avcodec_find_best_pix_fmt_of_2(enum AVPixelFormat dst_pix_fmt
 
 attribute_deprecated
 #if AV_HAVE_INCOMPATIBLE_LIBAV_ABI
-enum AVPixelFormat avcodec_find_best_pix_fmt2(enum AVPixelFormat *pix_fmt_list,
+enum AVPixelFormat avcodec_find_best_pix_fmt2(const enum AVPixelFormat *pix_fmt_list,
                                               enum AVPixelFormat src_pix_fmt,
                                               int has_alpha, int *loss_ptr);
 #else

libavcodec/imgconvert.c

@@ -248,7 +248,7 @@ enum AVPixelFormat avcodec_find_best_pix_fmt_of_2(enum AVPixelFormat dst_pix_fmt
 }
 
 #if AV_HAVE_INCOMPATIBLE_LIBAV_ABI
-enum AVPixelFormat avcodec_find_best_pix_fmt2(enum AVPixelFormat *pix_fmt_list,
+enum AVPixelFormat avcodec_find_best_pix_fmt2(const enum AVPixelFormat *pix_fmt_list,
                                             enum AVPixelFormat src_pix_fmt,
                                             int has_alpha, int *loss_ptr){
     return avcodec_find_best_pix_fmt_of_list(pix_fmt_list, src_pix_fmt, has_alpha, loss_ptr);