add proper destroy() and mark() vtables to PMCMatrix2D, like we should have had.
add proper destroy() and mark() vtables to PMCMatrix2D, like we should have had.

fernandobrito/parrot-linear-algebra,fernandobrito/parrot-linear-algebra,Whiteknight/parrot-linear-algebra,fernandobrito/parrot-linear-algebra,fernandobrito/parrot-linear-algebra,Whiteknight/parrot-linear-algebra