avformat/httpauth: add comment about "" and algorithm

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

libavformat/httpauth.c

@@ -224,8 +224,11 @@ static char *make_digest_auth(HTTPAuthState *state, const char *username,
     av_strlcatf(authstr, len, ",nonce=\"%s\"",     digest->nonce);
     av_strlcatf(authstr, len, ",uri=\"%s\"",       uri);
     av_strlcatf(authstr, len, ",response=\"%s\"",  response);
+
+    // we are violating the RFC and use "" because all others seem to do that too.
     if (digest->algorithm[0])
         av_strlcatf(authstr, len, ",algorithm=\"%s\"",  digest->algorithm);
+
     if (digest->opaque[0])
         av_strlcatf(authstr, len, ",opaque=\"%s\"", digest->opaque);
     if (digest->qop[0]) {