D7: editor multi-cursor support

Add secondary_cursors field to Editor with insert_char_multi,
delete_back_multi, delete_forward_multi methods. Right-to-left
processing ensures position shifts don't corrupt earlier insertions.

7 new tests: add/clear, all_positions, insert, delete_back,
delete_forward, unicode, duplicate-add.

local/recipes/tools/diffutils/source/lib/version-etc-fsf.c

@@ -0,0 +1,30 @@
+/* Variable with FSF copyright information, for version-etc.
+   Copyright (C) 1999-2006, 2009-2017 Free Software Foundation, Inc.
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+/* Written by Jim Meyering. */
+
+#include <config.h>
+
+/* Specification.  */
+#include "version-etc.h"
+
+/* Default copyright goes to the FSF. */
+
+const char version_etc_copyright[] =
+  /* Do *not* mark this string for translation.  %s is a copyright
+     symbol suitable for this locale, and %d is the copyright
+     year.  */
+  "Copyright %s %d Free Software Foundation, Inc.";