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/strtoull.m4

@@ -0,0 +1,24 @@
+# strtoull.m4 serial 7
+dnl Copyright (C) 2002, 2004, 2006, 2008-2017 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_STRTOULL],
+[
+  AC_REQUIRE([gl_STDLIB_H_DEFAULTS])
+  dnl We don't need (and can't compile) the replacement strtoull
+  dnl unless the type 'unsigned long long int' exists.
+  AC_REQUIRE([AC_TYPE_UNSIGNED_LONG_LONG_INT])
+  if test "$ac_cv_type_unsigned_long_long_int" = yes; then
+    AC_CHECK_FUNCS([strtoull])
+    if test $ac_cv_func_strtoull = no; then
+      HAVE_STRTOULL=0
+    fi
+  fi
+])
+
+# Prerequisites of lib/strtoull.c.
+AC_DEFUN([gl_PREREQ_STRTOULL], [
+  :
+])