ver 3.1.5
* Support framebuffer on Linux. (Experimental)
  (See doc/en/README.fb or doc/ja/README.fb in detail.)
* Support "?" of OSC 4, 10 and 11.
* Support CSI 14 t and CSI 18 t.
* Break the binary compatility of extra scrollbars and pixmap_engine
  with the ones before 3.1.4.
* Add "update_all" to the configuration protocol.
* Add k5 entry for ~/.mlterm/termcap.
* Bug fixes:
  Fix the incomplete hebavior of double- or triple-clicking and dragging.
  (Thanks to Andi Cristian Serbanescu)