NodeTypeDefDiff incorrectly handles multiple residual property definitions

The following change in node type definition should succeed:
old.cnd:

[my:nodetype]
- * (string)

new.cnd:

[my:nodetype]
- * (string)
- * (boolean)

But this fails. The reason is that property definitions are matched up using the name (in the case of residual property definitions *) as the key. In this case * (string) is matched up with * (boolean) and a change of property type is illegal, whereas it should have matched up with * (string) in which case there is no change in property type and in which case * (boolean) is a new property definition which is legal to add.