save xml file of the launch cmdline

Original commit message from CVS:
save xml file of the launch cmdline
diff --git a/tools/gstreamer-launch.c b/tools/gstreamer-launch.c
index 82a8d23..0b6cfa9 100644
--- a/tools/gstreamer-launch.c
+++ b/tools/gstreamer-launch.c
@@ -25,6 +25,8 @@
 
   gst_parse_launch (cmdline, GST_BIN (pipeline));
 
+  xmlSaveFile("gstreamer-launch.gst",gst_xml_write(pipeline));
+
   fprintf(stderr,"RUNNING pipeline\n");
   gst_element_set_state (pipeline, GST_STATE_PLAYING);