Function safe_app::ffi::nfs::dir_fetch_file

#[no_mangle]
pub unsafe extern "C" fn dir_fetch_file(
    app: *const App, 
    parent_info: *const MDataInfo, 
    file_name: *const c_char, 
    user_data: *mut c_void, 
    o_cb: extern "C" fn(user_data: *mut c_void, result: *const FfiResult, file: *const File, version: u64)
)

Retrieve file with the given name, and its version, from the directory.