Add sharing spec for Fiber and Thread -local variables

Author: eregon

spec/truffle/thread_safe_objects_spec.rb

@@ -255,4 +255,26 @@ def wb; @wb; end
     shared?(new_hash).should == true
   end
 
+  it "Fiber local variables which do not share the value" do
+    thread = Thread.current
+    shared?(thread).should == true
+
+    obj = Object.new
+    thread[:sharing_spec] = obj
+    begin
+      shared?(obj).should == false
+    ensure
+      thread[:sharing_spec] = nil
+    end
+  end
+
+  it "Thread local variables which share the value (probably they should not)" do
+    thread = Thread.current
+    shared?(thread).should == true
+
+    obj = Object.new
+    thread.thread_variable_set(:sharing_spec, obj)
+    shared?(obj).should == true # current non-ideal behavior
+  end
+
 end