Log Message:
Update skf to 1.99.6.

skf (1.99.6)

  * Fix typo on LWL error process
  * Fix cygwin python3 compilation

 -- Seiji Kaneko <efialtes@sourceforge.jp> Fri, 26 Jul 2013 23:13:36 +0900

skf (1.99.5)

  * Fix x-0213 unicode mapping
  * further nkf-compatibility
  * fix utf-16 code detection is escaping too early.
  * support UTF-32 input