visability propigation

[snowfoxsh]

One common design pattern is for all nested structures to have to same item visibility as the parent. Perhaps a syntax similar to the attribute propagation would be useful and not to far outside the scope of the project.

nest! {
    pub* struct First {
        f: struct Second {
            f: struct Third;
        }
    }
}

would expand to

pub struct First {
    f: Second,
}
pub struct Second {
    f: Third,
}
pub struct Third;

this feature would not cover field viability (#11) but would make another common design pattern easier to write without introducing a new syntax "concept".

[snowfoxsh]

This issue will be the parent issue for tracking visibility related improvements. The individual features should be referenced in their respective issues.