A bill signed by President Clinton Friday clears the way for a congressional pay boost, even though it never mentions giving lawmakers more money. The bill actually covers the Treasury Department and several other agencies, but under a 1989 law, members of Congress get cost-of-living raises unless they take action to prevent them. They have excluded themselves from such raises in this particular spending bill, from 1993 through last year, but this year they will get a 2.3 percent raise. One congressional watch dog group affiliated with Ralph Nader says House Speaker Newt Gingrich got exactly what he wanted. As Gary Ruskin of the Congressional Accountability Project sees it, Gingrich is giving himself and his overpaid colleagues a raise. Gingrich and Senate Republican Leader Trent Lott had no immediate comment.