anchor.diff:  { stdenv, fetchurl, intltool, pkgconfig, cmake
  -, ncurses, m17n_lib, m17n_db
  +, ncurses, m17n_lib, m17n_db, expat
   , withAnthy ? true, anthy ? null
   , withGtk ? true
   , withGtk2 ? withGtk, gtk2 ? null
  
positive.code:     "--with-skk"
      "--with-x"
      "--with-xft"
    ]
    ++ optional withAnthy "--with-anthy-utf8"
    ++ optional withGtk2 "--with-gtk2"
  
negative.code:     cmake
      m17n_lib
      m17n_db
      expat
    ]
    ++ optional withAnthy anthy
    ++ optional withGtk2 gtk2
  