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/fstat.m4

@@ -0,0 +1,38 @@
+# fstat.m4 serial 5
+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_FSTAT],
+[
+  AC_REQUIRE([AC_CANONICAL_HOST])
+  AC_REQUIRE([gl_SYS_STAT_H_DEFAULTS])
+
+  case "$host_os" in
+    mingw*)
+      dnl On this platform, the original stat() returns st_atime, st_mtime,
+      dnl st_ctime values that are affected by the time zone.
+      REPLACE_FSTAT=1
+      ;;
+  esac
+
+  dnl Replace fstat() for supporting the gnulib-defined open() on directories.
+  m4_ifdef([gl_FUNC_FCHDIR], [
+    gl_TEST_FCHDIR
+    if test $HAVE_FCHDIR = 0; then
+      case "$gl_cv_func_open_directory_works" in
+        *yes) ;;
+        *)
+          REPLACE_FSTAT=1
+          ;;
+      esac
+    fi
+  ])
+])
+
+# Prerequisites of lib/fstat.c and lib/stat-w32.c.
+AC_DEFUN([gl_PREREQ_FSTAT], [
+  AC_REQUIRE([gl_HEADER_SYS_STAT_H])
+  :
+])