When attempting to perform a != or NOT LIKE search on a multi-value CF,
with a value longer than 255 characters, the search limits the LEFT JOIN
based on the opposite condition.  However, it assumed the Content column
unless explicitly instructed; this means that, when checking against a
long string, it would return false positives.

For the case of !=, we can determine which of Content or LargeContent to
examine ahead of time.  Unfortunately, for NOT LIKE, we would be forced
to use a more complex limit to search both:

   Content LIKE '%value%' OR
   ((Content = '' OR Content IS NULL) AND LargeContent LIKE '%value%')

...and such a limit cannot be added to a LEFTJOIN clause using the
current DBIx::SearchBuilder.