dmd command line scripting experiments and observations

[Witold Baryluk]

Actually I do not think `DT varname = ...` will work. It will 
only work for a limited number of types, with value semantic. It 
will not work for reference types, and other non-trivial types 
(i.e. from libraries, phobos, arrays, etc). But for command line 
scripting I would still want to be able to use `auto` (via `:=` 
to `auto` translation) for them instead.