refactor - reduce CTFE memory consumption pt 1

Currently, CTFE allocates memory for every step in its computation. This can result in an enormous amount allocated. This is the first step towards using stack memory instead.
Congrats, here is the D translation:
```d
        scope __tmp = new RealExp(loc, -e1.toReal(), type);
        memcpy(&ue, cast(void*)__tmp, __traits(classInstanceSize, RealExp));
```
My eyes are bleeding.