Log Message:
Update textproc/ruby-rdtool package to 0.6.18 and it updates
devel/ruby-rd-mode pacakge, too.

= CHANGES
:0.6.18
  * bin/rd2 UTF-8 support.
  * support Ruby 1.9.
  * makerdtools.rb fixed some bugs.
  * fixed install dot.rd2rc problem
  * fixed some bugs.
:0.6.17
  * utils/rd-mode.el patch from <shirai@p1jp.com>
:0.6.16
  * utils/rd-mode.el font-face patch from HIRAOKA by MoonWolf \ 
<moonwolf@moonwolf.com>
:0.6.15
  * re-packaging by MoonWolf <moonwolf@moonwolf.com>