do not inline virtual destructors with d-pointers

do not inline virtual destructors with d-pointers

Reimplementing an inline method is opening a can of worms we don't want
to open if we ever want to us a d-pointer in those classes, so we do the
only thing which can save us from hell: move the destructors into the cc
sources and we are good.

Technically not an ABI break as the methods inline or not do the same
(nothing), so a program compiled against the old version still works
with the new version (beside that this version is still in experimental,
so nothing really has been build against this library anyway).

Git-Dch: Ignore