cocoa: add initial dialogs implementation from accSone (mantis #0025409)

git-svn-id: http://svn.freepascal.org/svn/lazarus/trunk@43523 4005530d-fff6-0310-9dd1-cebe43e6787f
cocoa: forgotten file

git-svn-id: http://svn.freepascal.org/svn/lazarus/trunk@43524 4005530d-fff6-0310-9dd1-cebe43e6787f