do not link against UI plugin. Showing UI in Ruby-bindings without y2base is no longer supported.
Remove workaround for ruby bug 4266 that is already fixed in ruby 2.0

Workaround caused broken ARGV constant when invoked ruby script that
require "yast".

link to ruby bug: http://bugs.ruby-lang.org/issues/show/4266
changes
changes with more rationale
Merge pull request #78 from yast/fix_argv2

Fix argv2