Update Vendored Rack to 1.2.0

Also update tests for itextomml 1.3.25.

vendor/plugins/rack/spec/spec_lock.rb

@@ -0,0 +1,36 @@
+require 'rack/lock'
+require 'rack/mock'
+
+class Lock
+  attr_reader :synchronized
+
+  def initialize
+    @synchronized = false
+  end
+
+  def synchronize
+    @synchronized = true
+    yield
+  end
+end
+
+describe Rack::Lock do
+  should "call synchronize on lock" do
+    lock = Lock.new
+    env = Rack::MockRequest.env_for("/")
+    app = Rack::Lock.new(lambda { |inner_env| }, lock)
+    lock.synchronized.should.equal false
+    app.call(env)
+    lock.synchronized.should.equal true
+  end
+
+  should "set multithread flag to false" do
+    app = Rack::Lock.new(lambda { |env| env['rack.multithread'] })
+    app.call(Rack::MockRequest.env_for("/")).should.equal false
+  end
+
+  should "reset original multithread flag when exiting lock" do
+    app = Rack::Lock.new(lambda { |env| env })
+    app.call(Rack::MockRequest.env_for("/"))['rack.multithread'].should.equal true
+  end
+end