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-sys_socket.c

@@ -0,0 +1,68 @@
+/* Test of <sys/socket.h> substitute.
+   Copyright (C) 2007, 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 Bruno Haible <bruno@clisp.org>, 2007.  */
+
+#include <config.h>
+
+#include <sys/socket.h>
+
+#include <errno.h>
+
+#if HAVE_SHUTDOWN
+/* Check some integer constant expressions.  */
+int a[] = { SHUT_RD, SHUT_WR, SHUT_RDWR };
+#endif
+
+/* Check that the 'socklen_t' type is defined.  */
+socklen_t t1;
+
+/* Check that the 'size_t' and 'ssize_t' types are defined.  */
+size_t t2;
+ssize_t t3;
+
+/* Check that 'struct iovec' is defined.  */
+struct iovec io;
+
+/* Check that a minimal set of 'struct msghdr' is defined.  */
+struct msghdr msg;
+
+int
+main (void)
+{
+  struct sockaddr_storage x;
+  sa_family_t i;
+
+  /* Check some errno values.  */
+  switch (ENOTSOCK)
+    {
+    case ENOTSOCK:
+    case EADDRINUSE:
+    case ENETRESET:
+    case ECONNABORTED:
+    case ECONNRESET:
+    case ENOTCONN:
+    case ESHUTDOWN:
+      break;
+    }
+
+  x.ss_family = 42;
+  i = 42;
+  msg.msg_iov = &io;
+
+  return (x.ss_family - i + msg.msg_namelen + msg.msg_iov->iov_len
+          + msg.msg_iovlen);
+}