Allocating byte aligned array

[timvol]

Hi guys,
how can I allocate an (e.g. 16) byte aligned array?
In C I can do the following:

     void *mem = malloc(1024+15);
     void *ptr = ((uintptr_t)mem+15) & ~ (uintptr_t)0x0F;
     memset_16aligned(ptr, 0, 1024);
     free(mem);

I think in D it looks similar to this:

     auto mem = new ubyte[1024+15];
     auto ptr = (mem.ptr + 15) & ~ (...???...) 0x0F;

How to fill ...???... ?
Without a cast, the compiler tells me that I the types are 
incompatible (ubyte* and int).

What's the correct syntax here?

PS: I don't want to use the experimental branch that provides 
alignedAllocate().