Showers are more than cramped cubbyholes these days. Separate stalls, once popular in the '30s and '40s, are back in style. Compared to the claustrophobic, fullyenclosed shower stalls of days gone by, shower enclosures now are larger, let in more light, and offer elaborate features such as multiple shower heads, bench seats, and steam. These 2-, 3-, and 4-sided glass surrounds open up the interior of the bathroom, eliminating the constricting mass of full-partition walls inside the bathroom. Even the styles, colors, and glazing patterns in combination tub/shower doors are so varied that virtually any taste can be satisfied. Price Vs. Quality At the low end are cheap-o tubenclosure kits for the do-it-yourselfer. These often cost less than $100. The professional who warrants his