gid parameters can be set to -1 to indicate that the original
owners must be kept. Change the types from uid_t/gid_t to a
long int (signed).
* libmisc/copydir.c: Change the copy_entry(), copy_dir(),
copy_symlink(), copy_special(), and copy_file() prototypes
accordingly.
* lib/prototypes.h: Add the parameters' name for the
libmisc/copydir.c functions.
* 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.
