Emit a no longer supported warning for gcoff* options.

	gcc/
	* common.opt (gcoff): Re-add as ignored option.
	(gcoff1, gcoff2, gcoff3): Likewise.

From-SVN: r254207

gcc/ChangeLog

 2017-10-29  Jim Wilson  <wilson@tuliptree.org>
 
+	* common.opt (gcoff): Re-add as ignored option.
+	(gcoff1, gcoff2, gcoff3): Likewise.
+
 	* Makefile.in (OBJS): Delete sdbout.o.
 	(GTFILES): Delete $(srcdir)/sdbout.c.
 	* debug.h: Delete sdb_debug_hooks.

gcc/common.opt

@@ -2872,6 +2872,22 @@ g
 Common Driver RejectNegative JoinedOrMissing
 Generate debug information in default format.
 
+gcoff
+Common Driver Ignore Warn(switch %qs no longer supported)
+Does nothing.  Preserved for backward compatibility.
+
+gcoff1
+Common Driver Ignore Warn(switch %qs no longer supported)
+Does nothing.  Preserved for backward compatibility.
+
+gcoff2
+Common Driver Ignore Warn(switch %qs no longer supported)
+Does nothing.  Preserved for backward compatibility.
+
+gcoff3
+Common Driver Ignore Warn(switch %qs no longer supported)
+Does nothing.  Preserved for backward compatibility.
+
 gcolumn-info
 Common Driver Var(debug_column_info,1) Init(1)
 Record DW_AT_decl_column and DW_AT_call_column in DWARF.