Avoid unaligned writes
Avoid unaligned writes

The result of `Data_custom_Val(caml_alloc_custom(...))` is word
aligned. `long double` and `long double complex` are usually
bigger. Such usage is even wrong on x86/amd64. Compilers are free to
use e.g. the MOVDQA instruction, if you tell them that your pointers are
properly aligned.

yallop/ocaml-ctypes,ocamllabs/ocaml-ctypes,ocamllabs/ocaml-ctypes,yallop/ocaml-ctypes