cpdup - roll 1.18 for ports consumers

* Add the -n option.  This is the not-for-real option.  cpdup will go through
  the motions but not actually take any action.  Useful for validating a
  topology without modifying it, e.g. 'cpdup -n -v -VV source target'.

* Fix clang static/global and alignment warnings

* Bump rev to 1.18

* Porters please note that this release has added an __aligned(n)
  directive to two structures.  BSDs and linux's should be able to
  handle this no-problem but just like __printflike() it is a bit
  of a departure from standard.

* Ports URL: fetch http://apollo.backplane.com/FreeBSDPorts/cpdup-1.18.tar.gz

Submitted-by: (static/global fixes) "Eitan Adler" <lists@eitanadler.com>
Submitted-by: (n-option & alignment fixes) dillon
Testing-by: "Eitan Adler" <lists@eitanadler.com>
Correct BSD License clause numbering from 1-2-4 to 1-2-3.

Apparently everyone's doing it:
http://svnweb.freebsd.org/base?view=revision&revision=251069

Submitted-by: "Eitan Adler" <lists at eitanadler.com>