Fix a bug when a method returns a reference.
Fix a bug when a method returns a reference.

If a method returns a reference (`function &f`), then the returned value
must be a variable. However, `return $return = …;` does not solve the
issue. We have to `$return = …; return $return;`. This is what this
patch does.

gpaton/atoum,mageekguy/atoum,CedCannes/atoum,jubianchi/atoum,vonglasow/atoum,mikaelrandy/atoum,mikaelrandy/atoum,CedCannes/atoum,agallou/atoum,Tiross/atoum,Tiross/atoum,vonglasow/atoum,gpaton/atoum,tejerka/atoum,jubianchi/atoum,tejerka/atoum,GuillaumeDievart/atoum,mageekguy/atoum,GuillaumeDievart/atoum,agallou/atoum