More intelligent code completion.

[mrshu]

Suppose we have written something like this in nxted

OnFwd(

Now what we write next will very probably be some kind of OUT_* constant. How come that our autocompletition system cannot suggest us that? We already have the information about this argument (docs say it's a motor and motor will be defined in terms of OUT_*) so it should be quite straightforward to implement this.

@Adman what do you think?

[Adman]

When we write OnFwd( it should show some "choosebox" that user can choose constant from it.