D calling convention

[Walter Bright]

Christian Kamm wrote:
> with the first parameter in EAX if possible, we'd have the neatness
> of "member function pointers have context as first arg" and the possibility
> of specifying left-to-right evaluation order easily. We'd lose the ability
> to pass hidden in EAX though.

EAX always gets the last argument evaluated, because evaluating an 
expression often naturally winds up in EAX.