(long_opts): Add --dereference, -L.

(long_opts): Add --dereference, -L.
(usage): Describe -L and -H.
(cp_option_init): Initialize to DEREF_UNDEFINED, not `1'.
(main): Add `H' and `-L' to getopt spec string.
[case 'a']: Initialize `dereference' to DEREF_NEVER, not 0.
[case 'd']: Likewise.
[case 'H']: New case.
[case 'L']: New case.
[case 'R']: Don't set dereference to `0' here.
If it's not yet defined, set x.dereference to DEREF_NEVER
if -R was specified, else set it to DEREF_ALWAYS.
Set x.xstat accordingly for -H.