Add the necessary includes, add an extra empty line for cosmetics

Originally committed as revision 23636 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavformat/http.h

@@ -18,9 +18,12 @@
  * License along with FFmpeg; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
+
 #ifndef AVFORMAT_HTTP_H
 #define AVFORMAT_HTTP_H
 
+#include "avio.h"
+
 /**
  * Sets custom HTTP headers.
  * A trailing CRLF ("\r\n") is required for custom headers.