Iterate all visible symbols, even from imported modules

[ketmar via Digitalmars-d-learn]

short answer: no.

there is still no way to write a reliable enumerator like this: 
too much things to hack around.

as for module symbols, it is easy: they has no type. literally: 
`!is(typeof(...))`.

`is(typeof(...))` is a necessary safeguard anyway if you are 
enumerating symbols in module, as you can't do much with module 
names anyway, and you *have* to filter 'em out with top-level 
static if.