Adding simple implicit return

Ruby return semantics are easy to grasp, not so easy to code. So many cases.
Added support for common cases, return const/variable or call.

lib/ruby/statements.rb

@@ -23,6 +23,9 @@ module Ruby
     def shift
       @statements.shift
     end
+    def pop
+      @statements.pop
+    end
     def [](i)
       @statements[i]
     end