Use usleep instead of sleep, some MinGW versions lack sleep.

Originally committed as revision 9044 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavformat/http.c

@@ -245,7 +245,7 @@ static int http_connect(URLContext *h, const char *path, const char *hoststr,
     s->off = 0;
     s->filesize = -1;
     if (post) {
-        sleep(1);
+        usleep(1000*1000);
         return 0;
     }