* libmisc/copydir.c: Split copy_tree() in more maintainable functions:
copy_entry(), copy_dir(), copy_symlink(), copy_hardlink(),
copy_special(), and copy_file().
* libmisc/copydir.c: -1 is used to indicate an error, directly set err
to -1, instead of incrementing it, and checking if not nul at the
end.
* NEWS: Document that usermod will now preserve user's file modification
and access time.
* libmisc/copydir.c: Preserve the access and modification time of copied
files. This is important for usermod. This will also impact useradd, for
the skeleton files, but this is not important.
* libmisc/copydir.c: Stop and return an error if a file could not be
closed after during a copy.
