Impossible to add widgets on some platforms

[mdawaffe]

The new multiwidgets use {time() . incrementor} as their widget ids in order to avoid collisions.

Those ids are over 2^33 which, on some platforms, causes array_map() inside add_magic_quotes( $_POST ) or stripslashes_deep( $_POST ) to mis-map those large array keys.

The end result is a mismatch between array keys and array values when trying to add widgets. The addition fails.

Attached changes the widget ids to be {( time() - 1199145600 ) . incrementor} (1199145600 is January 1st, 2008). This gives us about 27 years of breathing room before we run into the bug again (at least on the 2^33-limited box I was testing with).

(In [7281]) Avoid integer overflow with widget IDs. Props mdawaffe. fixes #6210