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/ioctl.m4

@@ -0,0 +1,41 @@
+# ioctl.m4 serial 4
+dnl Copyright (C) 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_IOCTL],
+[
+  AC_REQUIRE([gl_SYS_IOCTL_H_DEFAULTS])
+  AC_REQUIRE([gl_HEADER_SYS_SOCKET])
+  HAVE_IOCTL=1
+  if test "$ac_cv_header_winsock2_h" = yes; then
+    dnl Even if the 'socket' module is not used here, another part of the
+    dnl application may use it and pass file descriptors that refer to
+    dnl sockets to the ioctl() function. So enable the support for sockets.
+    HAVE_IOCTL=0
+  else
+    AC_CHECK_FUNCS([ioctl])
+    dnl On glibc systems, the second parameter is 'unsigned long int request',
+    dnl not 'int request'. We cannot simply cast the function pointer, but
+    dnl instead need a wrapper.
+    AC_CACHE_CHECK([for ioctl with POSIX signature],
+      [gl_cv_func_ioctl_posix_signature],
+      [AC_COMPILE_IFELSE(
+         [AC_LANG_PROGRAM(
+            [[#include <sys/ioctl.h>]],
+            [[extern
+              #ifdef __cplusplus
+              "C"
+              #endif
+              int ioctl (int, int, ...);
+            ]])
+         ],
+         [gl_cv_func_ioctl_posix_signature=yes],
+         [gl_cv_func_ioctl_posix_signature=no])
+      ])
+    if test $gl_cv_func_ioctl_posix_signature != yes; then
+      REPLACE_IOCTL=1
+    fi
+  fi
+])