multiple inclusion guard cleanup

Add missing multiple inclusion guards; clean up #endif comments;
add missing library prefixes; keep guard names consistent.

ffserver.h

@@ -18,11 +18,12 @@
  * License along with Libav; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
-#ifndef FFMPEG_FFSERVER_H
-#define FFMPEG_FFSERVER_H
+
+#ifndef LIBAV_FFSERVER_H
+#define LIBAV_FFSERVER_H
 
 /* interface between ffserver and modules */
 
 void ffserver_module_init(void);
 
-#endif /* FFMPEG_FFSERVER_H */
+#endif /* LIBAV_FFSERVER_H */