Missing 'const' in cast.

Originally committed as revision 11814 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavformat/http.c

@@ -219,7 +219,7 @@ static int http_connect(URLContext *h, const char *path, const char *hoststr,
     /* send http header */
     post = h->flags & URL_WRONLY;
     auth_b64 = av_malloc(auth_b64_len);
-    av_base64_encode(auth_b64, auth_b64_len, (uint8_t *)auth, strlen(auth));
+    av_base64_encode(auth_b64, auth_b64_len, (const uint8_t *)auth, strlen(auth));
     snprintf(s->buffer, sizeof(s->buffer),
              "%s %s HTTP/1.1\r\n"
              "User-Agent: %s\r\n"