m4/gst.m4: Add

m4/gst.m4: Add

Original commit message from CVS:
* m4/gst.m4:
Add
* m4/gst-arch.m4:
* m4/gst-args.m4:
* m4/gst-check.m4:
* m4/gst-debuginfo.m4:
* m4/gst-default.m4:
* m4/gst-doc.m4:
* m4/gst-error.m4:
* m4/gst-feature.m4:
* m4/gst-function.m4:
* m4/gst-gettext.m4:
* m4/gst-glib2.m4:
* m4/gst-libxml2.m4:
* m4/gst-parser.m4:
* m4/gst-plugin-docs.m4:
* m4/gst-plugindir.m4:
* m4/gst-valgrind.m4:
* m4/gst-x11.m4:
Convert all macros to use AG_GST style so we can properly warn
when they're missing if configure.ac calls AG_GST_INIT
Will require update in all GStreamer modules.