r175587 - Add a new 'type_visibility' attribute to allow users to

[Rafael Espíndola]

> Add a new 'type_visibility' attribute to allow users to
> control the visibility of a type for the purposes of RTTI
> and template argument restrictions independently of how
> visibility propagates to its non-type member declarations.

Could you pleas add a bit of user documentation on to how this should
be used? What is the intended use case? Exporting a class with only
virtual methods? If so, shouldn't the constructors also get the type
visibility?

Cheers,
Rafael