libx265: Bump version requirement

Build 13 has a crucial fix which makes x265_encode_headers work
as its always been documented.

Previous to this, the check was incorrect.

Also allows for use of the repeat headers flag.
Signed-off-by: Derek Buitenhuis <derek.buitenhuis@gmail.com>

configure

@@ -4616,8 +4616,8 @@ enabled libx264           && require libx264 x264.h x264_encoder_encode -lx264 &
                              { check_cpp_condition x264.h "X264_BUILD >= 118" ||
                                die "ERROR: libx264 must be installed and version must be >= 0.118."; }
 enabled libx265           && require_pkg_config x265 x265.h x265_encoder_encode &&
-                             { check_cpp_condition x265.h "X265_BUILD >= 9" ||
-                               die "ERROR: libx265 version must be >= 9."; }
+                             { check_cpp_condition x265.h "X265_BUILD >= 13" ||
+                               die "ERROR: libx265 version must be >= 13."; }
 enabled libxavs           && require libxavs xavs.h xavs_encoder_encode -lxavs
 enabled libxvid           && require libxvid xvid.h xvid_global -lxvidcore
 enabled libzmq            && require_pkg_config libzmq zmq.h zmq_ctx_new