Whoa! Wrapup reported in last month's issue that General Motors Corp. intended to halt production this summer of its boulevard boats -- the Buick Roadmaster, Cadillac Fleetwood and Chevrolet's Caprice and Impala SS. We were wrong. GM says production of its land yachts will be halted not this summer, but the summer of 1996. So for all those folks who like the feel of the ocean while driving down the highway, you've got one more year to get your boats. And, of course, WAW regrets the miscue.