Fix error in date_convert() that threw out a unix date with a zero value.

In the PHP4 date_create, need to test for a unix timestamp before trying the loose regex or unix timestamps get treated as iso dates.

More cleanup of PHP4 wrapper functions. We can get most things right except that there is no reliable way to get daylight savings time right in PHP4.

The 'loose' regex wasn't quite loose enough. It should also allow for an input format that has hours and minutes but no seconds.