LEADERS OF G.O.P. REACH COMPROMISE ON A TAX-CUT BILL
Republican leaders reach general agreement on plan that would cut taxes by $792 billion over next decade; under plan, which draws from tax bills recently passed in House and Senate, all income tax rates would be reduced by one percentage point; plan also includes reduction in top rate on capital gains to 18 percent from 20 percent; it would provide tax break for many married couples, and would phase out inheritance tax on large estates; Pres Clinton has promised to veto vill; photo (M)