tsi() compares $time as integer.

Avoids errors caused by invalid $time value. In places
Textpattern itself uses way strange values as the $time.
For instance on articles panel it defaults to SQL,
NULLDATETIME.

git-svn-id: http://textpattern.googlecode.com/svn/development/4.x@5266 2fea6a4d-a838-0410-917b-93a53c48e9d2