Republicans and Democrats agreed Tuesday on a $1.1 trillion spending bill to avoid a government shutdown and delay a politically charged struggle over President Obama’s new immigration policy until the new year. In an unexpected move, lawmakers also agreed on legislation expected to be incorporated into the spending measure that will permit a reduction in benefits for current retirees at economically distressed multi-employer pension plans. Supporters said it was part of an effort to prevent a slow-motion collapse of a system that provides retirement income to millions, but critics objected vehemently. There was no immediate reaction from the White House to the bill. House Speaker John Boehner said he hoped for a vote on the measure Thursday.