Datepicker constrainInput Option

Datepicker constrainInput Option


The documentation for the Datepicker widget includes the option
"constrainInput". I do not see this option in the source code for
ui.datepicker.js versions 1.5.2 or 1.6 RC2. Am a missing something or
has the version supporting this option not yet been released?
http://docs.jquery.com/UI/Datepicker/datepicker#options
http://ui.jquery.com/bugs/changeset/755
Any assistance is appreciated.