Macro rucky::import

macro_rules! import {
    () => { ... };
    ( $pkg:path ) => { ... };
    ( $root:ident * ) => { ... };
    ( $root:ident :: $($tail:ident)::+ * ) => { ... };
    ( $pkg:path ; $( $rest:tt )* ) => { ... };
    (
        $root:ident { $( $member:ident ),+ } ;
        $( $rest:tt )*
    ) => { ... };
    (
        $root:ident :: $($tail:ident)::+ *;
        $( $rest:tt )*
    ) => { ... };
    (
        $root:ident :: $($tail:ident)::+
        { $( $member:ident ),+ } ;
        $( $rest:tt )*
    ) => { ... };
}

Macro to generate use statement at once.