move machine to module level

makes for shorter, more concise, access
also remove one more bug possibility
(reinitiation)

lib/register/passes/call_implementation.rb

@@ -23,5 +23,5 @@ module Register
       end
     end
   end
-  Virtual::Machine.instance.add_pass "Register::CallImplementation"
+  Virtual.machine.add_pass "Register::CallImplementation"
 end

lib/register/passes/return_implementation.rb

@@ -18,5 +18,5 @@ module Register
       end
     end
   end
-  Virtual::Machine.instance.add_pass "Register::ReturnImplementation"
+  Virtual.machine.add_pass "Register::ReturnImplementation"
 end

lib/register/passes/set_implementation.rb

@@ -42,5 +42,5 @@ module Register
       end
     end
   end
-  Virtual::Machine.instance.add_pass "Register::SetImplementation"
+  Virtual.machine.add_pass "Register::SetImplementation"
 end