100l, compute correctly poll_table size when allocating

Originally committed as revision 15238 to svn://svn.ffmpeg.org/ffmpeg/trunk

ffserver.c

@@ -545,7 +545,7 @@ static int http_server(void)
     struct pollfd *poll_table, *poll_entry;
     HTTPContext *c, *c_next;
 
-    if(!(poll_table = av_mallocz(nb_max_http_connections + 2))) {
+    if(!(poll_table = av_mallocz((nb_max_http_connections + 2)*sizeof(*poll_table)))) {
         http_log("Impossible to allocate a poll table handling %d connections.\n", nb_max_http_connections);
         return -1;
     }