Function proto_tree_add_string_format_value 

pub unsafe extern "C" fn proto_tree_add_string_format_value(
    tree: *mut proto_tree,
    hfindex: c_int,
    tvb: *mut tvbuff_t,
    start: gint,
    length: gint,
    value: *const c_char,
    format: *const c_char,
    ...
) -> *mut proto_item