quercus protected field set in subclass

git-svn-id: svn://svn.caucho.com/home/svn/svnroot/resin/trunk@10284 9c94448d-38f1-0310-a231-d98308ff1ebf
quercus add DateTimeInterface super class

git-svn-id: svn://svn.caucho.com/home/svn/svnroot/resin/trunk@10285 9c94448d-38f1-0310-a231-d98308ff1ebf
quercus add date_diff() alias

git-svn-id: svn://svn.caucho.com/home/svn/svnroot/resin/trunk@10286 9c94448d-38f1-0310-a231-d98308ff1ebf