Write page : timestamp checkbox is useless

[xibe]

The Edit Timestamp checkbox in the Edit Post admin page is useless at best, un-ergnomic at worst. The date should simply be updated if the date field submited is different from the recorded one. As long as the date is not changed, there is no need for the date to be updated.

I think this functionality would benefit from having the checkbox replaced by a simple date comparison between the submited date and the one already in MySQL.

About time this is fixed. I think we need a post-screen overhaul after 2.0.1 anyway.