configure: replace deprecated AM_CONFIG_HEADER with AC_CONFIG_HEADERS
configure: replace deprecated AM_CONFIG_HEADER with AC_CONFIG_HEADERS

AM_CONFIG_HEADER has been removed in the just-released automake 1.13:
https://lists.gnu.org/archive/html/automake/2012-12/msg00038.html

https://bugzilla.gnome.org/show_bug.cgi?id=690881

StreamUtils/gst-plugins-ugly,GStreamer/gst-plugins-ugly,krieger-od/gst-plugins-ugly,cablelabs/gst-plugins-ugly,StreamUtils/gst-plugins-ugly,freedesktop-unofficial-mirror/gstreamer__gst-plugins-ugly,Lachann/gst-plugins-ugly,shelsonjava/gst-plugins-ugly,collects/gst-plugins-ugly,krieger-od/gst-plugins-ugly,freedesktop-unofficial-mirror/gstreamer__gst-plugins-ugly,reynaldo-samsung/gst-plugins-ugly,jpakkane/gstreamer-plugins-ugly,reynaldo-samsung/gst-plugins-ugly,krieger-od/gst-plugins-ugly,cablelabs/gst-plugins-ugly,Kurento/gst-plugins-ugly,StreamUtils/gst-plugins-ugly,reynaldo-samsung/gst-plugins-ugly,GrokImageCompression/gst-plugins-ugly,collects/gst-plugins-ugly,Lachann/gst-plugins-ugly,surround-io/gst-plugins-ugly,surround-io/gst-plugins-ugly,jar1karp/gst-plugins-ugly,Kurento/gst-plugins-ugly,GrokImageCompression/gst-plugins-ugly,shelsonjava/gst-plugins-ugly,Kurento/gst-plugins-ugly,sebras/gst-plugins-ugly,freedesktop-unofficial-mirror/gstreamer__gst-plugins-ugly,collects/gst-plugins-ugly,GStreamer/gst-plugins-ugly,shelsonjava/gst-plugins-ugly,sebras/gst-plugins-ugly,GrokImageCompression/gst-plugins-ugly,Lachann/gst-plugins-ugly,jpakkane/gstreamer-plugins-ugly,jar1karp/gst-plugins-ugly,cablelabs/gst-plugins-ugly,krieger-od/gst-plugins-ugly,jar1karp/gst-plugins-ugly,sebras/gst-plugins-ugly,surround-io/gst-plugins-ugly,jpakkane/gstreamer-plugins-ugly,collects/gst-plugins-ugly,GStreamer/gst-plugins-ugly