sandbox r50, here we go, loading conflicting gems

Checky.

  require 'sandbox'
  
  hpricot = Sandbox.new :init => [:all]
  hpricot.eval(%{
    require 'rubygems'
    require_gem 'hpricot', '=0.4.47'
    require 'hpricot'
    puts Hpricot("<a class=test>link</a>").search(".test")
  })
  
  hpricot2 = Sandbox.new :init => [:all]
  hpricot2.eval(%{
    require 'rubygems'
    require_gem 'hpricot', '=0.4'
    require 'hpricot'
    puts Hpricot("<a class=test>link</a>").search(".test")
  })

This proves existence of a bug in Hpricot 0.4, which was extinguished in 0.4.47.
The output is:

  <a class="test">link</a>
  /home/why/sand/RUBY-1_8_5/lib/ruby/gems/1.8/gems/hpricot-0.4/lib/hpricot/traverse.rb:110:in
  `_eval': NoMethodError: undefined method `[]=' for #<MatchData:0x8510448>
  (Sandbox::Exception)
          from ./lib/sandbox.rb:19:in `eval'
          from test.rb:21

In other words, 0.4.47 finds the link, but 0.4 raises the MatchData exception.

This new version requires a new patch.  Indeed, swapping ruby_cref was the
finishing touch.  Be aware, some globals and constants are not yet implemented.

_why