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/gnulib-tests/test-raise.c

@@ -0,0 +1,50 @@
+/* Test raising a signal.
+   Copyright (C) 2011-2017 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/>.  */
+
+#include <config.h>
+
+#include <signal.h>
+
+#include "signature.h"
+SIGNATURE_CHECK (raise, int, (int));
+
+#include <stdlib.h>
+
+#include "macros.h"
+
+/* It is safe to use _Noreturn here: exit() never returns, and GCC knows that
+   exit() is a non-returning function, even on platforms where its declaration
+   in <stdlib.h> does not have the 'noreturn' attribute.  */
+static _Noreturn void
+handler (int sig)
+{
+  exit (0);
+}
+
+int
+main (void)
+{
+  /* Test behaviour for invalid argument.  */
+  ASSERT (raise (-1) != 0);
+
+  /* Test behaviour for SIGINT.  */
+  ASSERT (signal (SIGINT, handler) != SIG_ERR);
+
+  raise (SIGINT);
+
+  /* We should not get here, because the handler takes away the control.  */
+  exit (1);
+}