(enum) [NO_DEREFERENCE_OPTION]: New member.

(enum) [NO_DEREFERENCE_OPTION]: New member.
(enum) [NO_PRESERVE_ATTRIBUTES_OPTION]: New member.
(enum) [PRESERVE_ATTRIBUTES_OPTION]: New member.
(long_opts): Separate -d and --no-dereference options.
Add `no-preserve'.
Separate -p and --preserve options.
The long-named --preserve now accepts optional arguments; -p doesn't.
(usage): Describe additions and changes.
(cp_option_init): Initialize new member, preserve_links, to 0.
(decode_preserve_arg): New function.
(main) [case 'a']: Set preserve_links to 1.
[case 'd']: Set preserve_links to 1.
Add `case' for long-named --no-dereference.
Handle long-named --no-preserve and --preserve.