Alignment of dynamic arrays

[Luc Bourhis via Digitalmars-d]

With "auto a = new double[1000]", is there any guarantee that  
a.ptr is aligned on a 16-byte boundary? Indeed I would like to 
use core.simd and this alignment is paramount for efficient 
loading from memory to SSE2 registers.

On MacOS X and 64-bit Linux, it looks true for dmd. Looking at 
the implementation of arrays, it seems that it eventually depends 
on gc_malloc implementation but I could not find the code of that 
extern(C) function.