* libmisc/copydir.c, src/usermod.c, lib/prototypes.h: The uid and

* libmisc/copydir.c, src/usermod.c, lib/prototypes.h: The uid and
  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.