* configure.in: Remove references to unsupported systems.

* configure.in: Remove references to unsupported systems.

* notes/copyright:
* MAINTAINERS: Remove references to files that have been removed.

* os.texi (System Environment): Remove references to OSes that are
not supported anymore.

* PROBLEMS:
* MACHINES: Remove references to systems not supported anymore.

* makefile.w32-in:
* Makefile.in: Remove references to Xenix.

* gnus.el (gnus-use-long-file-name): Remove reference to xenix.

* obsolete/x-apollo.el: Remove file for unsupported system.

* term/x-win.el (vendor-specific-keysyms): Remove reference to
Apollo.

* progmodes/gud.el (gud-dgux-p): Remove.
(dbx): Remove reference to dgux.

* progmodes/ps-mode.el (ps-mode-print-function):
* ps-print.el (ps-lp-system):
* paths.el (rmail-spool-directory):
* ls-lisp.el (ls-lisp-emulation):
* lpr.el (lpr-lp-system):
* dired.el (dired-chown-program): Remove references to dgux.

* m/7300.h:
* m/acorn.h:
* m/alliant-2800.h:
* m/alliant.h:
* m/alliant1.h:
* m/alliant4.h:
* m/altos.h:
* m/amdahl.h:
* m/apollo.h:
* m/att3b.h:
* m/aviion-intel.h:
* m/aviion.h:
* m/celerity.h:
* m/clipper.h:
* m/cnvrgnt.h:
* m/convex.h:
* m/cydra5.h:
* m/delta88k.h:
* m/dpx2.h:
* m/dual.h:
* m/elxsi.h:
* m/f301.h:
* m/gould-np1.h:
* m/gould.h:
* m/i860.h:
* m/ibmps2-aix.h:
* m/ibmrt-aix.h:
* m/ibmrt.h:
* m/irist.h:
* m/is386.h:
* m/isi-ov.h:
* m/mega68.h:
* m/mg1.h:
* m/news-r6.h:
* m/news-risc.h:
* m/news.h:
* m/nh3000.h:
* m/nh4000.h:
* m/ns16000.h:
* m/ns32000.h:
* m/nu.h:
* m/orion.h:
* m/orion105.h:
* m/paragon.h:
* m/pfa50.h:
* m/plexus.h:
* m/pyramid.h:
* m/pyrmips.h:
* m/sh3el.h:
* m/sps7.h:
* m/sr2k.h:
* m/stride.h:
* m/sun1.h:
* m/sun2.h:
* m/sun3-68881.h:
* m/sun3-fpa.h:
* m/sun3-soft.h:
* m/sun3.h:
* m/sun386.h:
* m/symmetry.h:
* m/tad68k.h:
* m/tahoe.h:
* m/targon31.h:
* m/tek4300.h:
* m/tekxd88.h:
* m/tower32.h:
* m/tower32v3.h:
* m/ustation.h:
* m/wicat.h:
* m/xps100.h:
* s/cxux.h:
* s/cxux7.h:
* s/dgux.h:
* s/dgux4.h:
* s/dgux5-4-3.h:
* s/dgux5-4r2.h:
* s/esix.h:
* s/esix5r4.h:
* s/hiuxmpp.h:
* s/hiuxwe2.h:
* s/iris3-5.h:
* s/iris3-6.h:
* s/isc2-2.h:
* s/isc3-0.h:
* s/isc4-0.h:
* s/isc4-1.h:
* s/newsos5.h:
* s/newsos6.h:
* s/osf1.h:
* s/osf5-0.h:
* s/riscix1-1.h:
* s/riscix12.h:
* s/sco4.h:
* s/sco5.h:
* s/sunos4-0.h:
* s/sunos4-1.h:
* s/sunos413.h:
* s/sunos4shr.h:
* s/umax.h:
* s/unipl5-2.h:
* s/xenix.h:
* cxux-crt0.s:
* unexapollo.c:
* unexconvex.c:
* unexenix.c:
* unexsni.c: Remove files for systems no longer supported.

* m/intel386.h: Remove references to unsupported systems.

* w32.c (get_emacs_configuration): Remove reference to i860.

* sysdep.c: Remove dead code.