http: Support relative URL redirection

In RFC 2616, this was explicitly said to be an absolute URL,
while in an upcoming draft [1] it is allowed to be relative as well.

[1] http://tools.ietf.org/html/draft-ietf-httpbis-p2-semantics-25#section-7.1.2Signed-off-by: Martin Storsjö <martin@martin.st>

libavformat/http.c

@@ -335,7 +335,10 @@ static int process_line(URLContext *h, char *line, int line_count,
         while (av_isspace(*p))
             p++;
         if (!av_strcasecmp(tag, "Location")) {
-            av_strlcpy(s->location, p, sizeof(s->location));
+            char redirected_location[MAX_URL_SIZE];
+            ff_make_absolute_url(redirected_location, sizeof(redirected_location),
+                                 s->location, p);
+            av_strlcpy(s->location, redirected_location, sizeof(s->location));
             *new_location = 1;
         } else if (!av_strcasecmp (tag, "Content-Length") && s->filesize == -1) {
             s->filesize = strtoll(p, NULL, 10);