Small correction to defaultLongDateFormat (hours)

The old jQuery.format.date.defaultLongDateFormat used hh: two-digit 12-hour time, but had no "am/pm" marker, which made it ambiguous.  

Switching to HH: two-digit 24-hour time.

New format isn't ambiguous, doesn't make the result string longer, and is compatible with (among other things) MySQL datetime formatting.