MANCHESTER, N.H. -- Governor Mitt Romney, under fire for an adviser's remark that he has been ''faking" his support of abortion rights, insisted yesterday that he would not back off his 2002 campaign pledge to uphold Massachusetts abortion laws, saying, ''I take my promises very seriously." The Republican governor and possible 2008 presidential contender was forced to deal with questions about his abortion position during a trip to this key primary state a day after his top political consultant, Michael Murphy, was quoted in the conservative National Review as saying that Romney has been ''a prolife Mormon faking it as...