WASHINGTON — The FBI interviewed Hillary Clinton on Saturday about her use of a private email server while she was secretary of state, her campaign announced after the meeting, as federal investigators neared the end of the probe that has hung over her White House bid. Clinton, the Democratic presidential candidate, gave a voluntary interview for 3 1/2 hours at FBI headquarters in Washington, her campaign said. "I've been eager to do it, and I was pleased to have the opportunity to assist the department in bringing its review to a conclusion," Clinton said in describing the FBI session to NBC's "Meet the Press" for an interview to air Sunday.