A goopy white mess smeared the inside of the Double Stuf Oreo
package. The cookies' creamy center had oozed out, leaving a
tumble of dark chocolate wafers.    • Related   • &nbsp;   In
the Kraft Foods laboratory where cookies get the snack-world
equivalent of an automobile crash test, this experimental Oreo
was totaled. The flop last year delayed efforts to purge the
cookie of trans fat, yet another in a stream of dietary
villains.  The Oreo is but one example of a foodmaker's attempts
to reinvent its fattening fare. Food fads and conflicting
research force Northfield-based Kraft and other foodmakers to
shift gears from one new product to another, in an endless quest
to develop the next big thing out of the same old things: sugar,
flour and fat.  Often, the result leaves consumers confused,
struggling to make sense of a plethora of new creations and to
decode small type on colorful packages. "Not for weight
control," warns a box of sugar-free Oreos that also is labeled
"Sensible Snacking."  For a fickle publi