avformat/utils: add const for argument passed to ff_is_http_proto()

Signed-off-by: Limin Wang <lance.lmwang@gmail.com>

libavformat/internal.h

@@ -907,7 +907,7 @@ void ff_format_io_close(AVFormatContext *s, AVIOContext **pb);
  * @param s AVFormatContext
  * @param filename URL or file name to open for writing
  */
-int ff_is_http_proto(char *filename);
+int ff_is_http_proto(const char *filename);
 
 /**
  * Parse creation_time in AVFormatContext metadata if exists and warn if the

libavformat/utils.c

@@ -1802,7 +1802,7 @@ void ff_format_io_close(AVFormatContext *s, AVIOContext **pb)
     *pb = NULL;
 }
 
-int ff_is_http_proto(char *filename) {
+int ff_is_http_proto(const char *filename) {
     const char *proto = avio_find_protocol_name(filename);
     return proto ? (!av_strcasecmp(proto, "http") || !av_strcasecmp(proto, "https")) : 0;
 }