loplugin-passbyref: ignore non-base declarations

Only consider base declarations, not overriden ones, or we warn on methods that
are overriding stuff from external libraries.

Change-Id: I08791c96f7adba5997ad237a98e7c08a759042ad
remove unnecessary use of OUString constructor

Change-Id: I7769625289d8bf47fe5905dfb91d3bce9e0f5c85