Macro dync::into_dyn

macro_rules! into_dyn {
    (Slice < dyn $trait:path >) => { ... };
    (SliceMut < dyn $trait:ident >) => { ... };
    (VecDyn < dyn $trait:ident >) => { ... };
    (SliceCopy < dyn $trait:ident >) => { ... };
    (SliceCopyMut < dyn $trait:ident >) => { ... };
    (VecCopy < dyn $trait:ident >) => { ... };
    (@owned $vec:ident < dyn $trait:ident >) => { ... };
    (@slice $slice:ident < dyn $trait:path >) => { ... };
}

Convert a given container type (e.g. VecCopy or SliceDyn) to have a dynamic VTable.