Datepicker: Accept two year digits from the text input event when expecting 'yy'

Since 1.11, parseDate() doesn't accept a date with two year digits when the format expects 'yy'. That's nice.
But when a user enters a date in the text input of a datepicker, the widget should understand the date even if the user enters a two year digits. Indeed, the users may easily enter a two year digits date (quicker) even if we finally expect four year digits.

May I suggest this:
 - Be more permissive when parsing the year from the text input without changing the new behaviour of the parseDate() function.
 - Format the date correctly on change() event (per example), transforming the year in the real expected format (two or four digits) if needed.

The datepicker is, since 1.11, too restrictive for the text input and some users don't understand why their input is not understood by the datepicker.