* pango/src/layoutiter.[hg|ccg]: PangoLayoutIter became a boxed type at some
	point, with a pango_layout_iter_copy() function, so we can now wrap it
	normally without so much hand-coding. This also adds a copy constructor.
	* pango/src/layout.ccg: get_iter(): Use the LayoutIter copy constructor
	instead of the crappy old assign_gobj() function. Also deprecate this
	method, adding a get_iter(void), now that the copy constructor allows us to
	use LayoutIter as a return type.