Log Message:
shells/yash: update to 2.56.1

# changes

* Codebase moved from OSDN to github.
* The shell can now open more file descriptors on Cygwin.
* Fixed the bug where the "typeset -fp" built-in prints parameter
  expansions of the form ${foo:/bar/baz} with a redundant # flag like
  ${foo:/#bar/baz}.
* Fixed the bug where the emacs-capitalize-word line-editing command
  misbehaves and possibly crashes the shell if there is no word following
  the cursor to be capitalized.
* Added the emacs-search-forward-current and emacs-search-backward-current
  line-editing commands. (by @vext01 in #37)
* [line-editing] Added the completion script for doas. (by @DanisDGK in #45)