Very low level class to tune some aspects of the garbage collector. Actually,
NATIVE_ARRAY_COLLECTOR is useful only for classes using attribute(s) of type NATIVE_ARRAY
and must be used only by expert people. This is very low level and the goal is to achieve the
very best performances.
Forces the garbage collector to continue the marking process on the index-th element of
the native_array. The element at index can be Void or not Void (the Void-ness test
performed inside the mark_item itself).