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_wait.h

@@ -0,0 +1,53 @@
+/* Test of macros shared between <sys/wait.h> and <stdlib.h>.
+   Copyright (C) 2010-2017 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 Eric Blake <ebb9@byu.net>, 2010.  */
+
+static int
+test_sys_wait_macros (void)
+{
+  /* Check subset of <sys/wait.h> macros that must be visible here.
+     Note that some of these macros are only portable when operating
+     on an lvalue.  */
+  int i;
+  for (i = 0; i < 0x8000; i = (i ? i << 1 : 1))
+    {
+      /* POSIX requires that for all valid process statuses, that
+         exactly one of these three macros is true.  But not all
+         possible 16-bit values map to valid process status.
+         Traditionally, 8 of the bits are for WIFEXITED, 7 of the bits
+         to tell between WIFSIGNALED and WIFSTOPPED, and either 0x80
+         or 0x8000 to flag that core was also dumped.  Since we don't
+         know which byte is WIFEXITED, we skip the both possible bits
+         that can signal core dump.  */
+      if (i == 0x80)
+        continue;
+      if (!!WIFSIGNALED (i) + !!WIFEXITED (i) + !!WIFSTOPPED (i) != 1)
+        return 1;
+    }
+  i = WEXITSTATUS (i) + WSTOPSIG (i) + WTERMSIG (i);
+
+  switch (i)
+    {
+#if 0
+  /* Gnulib doesn't guarantee these, yet.  */
+    case WNOHANG:
+    case WUNTRACED:
+#endif
+      break;
+    }
+  return 0;
+}