Fixed a critical bug in the runtime, where _d_allocmemoryT would mark the memory block as having pointers (for scanning) opposite of what it should. So pointers would not be seen and freed. Should fix a bunch of regressions with AAs.

module tangotests.mem3;

void main()
{
    int[] arr;
    arr ~= [1,2,3];
    assert(arr[0] == 1);
    assert(arr[1] == 2);
    assert(arr[2] == 3);
    delete arr;
    assert(arr is null);
}