* oln/core/abstract/image.hh (packed_vtypes): Remove.
	(packed_vtypes<category::image, I>): Use mlc::assert to test the
	virtual types.
	Aesthetic changes.
	(image::~image): Check the vtypes thanks to
	packed_vtypes<category::image, I>.


git-svn-id: https://svn.lrde.epita.fr/svn/oln/trunk@468 4aad255d-cdde-0310-9447-f3009e2ae8c0