#22 Fix for JS error on adding new calendar events

[KFleshman]

When adding an event to the calendar in 0.96.2, a
JavaScript error of "evenstart_hidden.value is null or
not an object" or "frm.eventstart_hidden has no
properties" occurrs in IE and Firefox, respectively.
It would appear that
modules/calendarmodule/js/postedit.validate.js still
has remnants of from when the calendar had two date
selection boxes. My fix is to comment out the portion
that checks for differing dates, since there is now
only one date field.

[KFleshman]

Updated postedit.validate.js