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/m4/raise.m4

@@ -0,0 +1,36 @@
+# raise.m4 serial 4
+dnl Copyright (C) 2011-2017 Free Software Foundation, Inc.
+dnl This file is free software; the Free Software Foundation
+dnl gives unlimited permission to copy and/or distribute it,
+dnl with or without modifications, as long as this notice is preserved.
+
+AC_DEFUN([gl_FUNC_RAISE],
+[
+  AC_REQUIRE([gl_SIGNAL_H_DEFAULTS])
+  AC_REQUIRE([AC_CANONICAL_HOST])
+  AC_CHECK_FUNCS([raise])
+  if test $ac_cv_func_raise = no; then
+    HAVE_RAISE=0
+  else
+    m4_ifdef([gl_MSVC_INVAL], [
+      AC_REQUIRE([gl_MSVC_INVAL])
+      if test $HAVE_MSVC_INVALID_PARAMETER_HANDLER = 1; then
+        REPLACE_RAISE=1
+      fi
+    ])
+    m4_ifdef([gl_SIGNALBLOCKING], [
+      gl_SIGNALBLOCKING
+      if test $HAVE_POSIX_SIGNALBLOCKING = 0; then
+        m4_ifdef([gl_SIGNAL_SIGPIPE], [
+          gl_SIGNAL_SIGPIPE
+          if test $gl_cv_header_signal_h_SIGPIPE != yes; then
+            REPLACE_RAISE=1
+          fi
+        ], [:])
+      fi
+    ])
+  fi
+])
+
+# Prerequisites of lib/raise.c.
+AC_DEFUN([gl_PREREQ_RAISE], [:])