porting GCC macro to D

[ketmar]

> You can hack around that limitation if it's acceptable to use a 
> temporary variable:
sure, and i can rewrite the whole call, passing destination 
variable as template argument. but this looks ugly.

thanx for the answer anyway (and bearophile too).

> Unfortunately, you cannot use template mixins for this, because 
> they can only contain declarations, not statements.
yes, i found that hard way — with experiments. it's a pity, i 
think.