NEW WRITER: InStyle has named another guest columnist. Actress Megan Mullally, the vicious librarian in “Parks and Recreation,” is penning a regular back-page column titled “Last Laugh.” In the debut column, which appears in the January issue on newsstands Dec. 14, Mullally itemizes her New Year’s resolutions, like “Launch my celebrity fragrance, A Whiff of Megan.” InStyle already has Rebecca Minkoff doing the monthly “Ask a Designer” column.