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.
Can you encapsulate the emplacement new (to help yebblies with ddmd), e.g. `emplace(&ue, RealExp(local, -e1->to real(), type);`.
Emplace could either be a template function or a macro.