Boston Mayor Thomas M. Menino will head to the Democratic National Convention in Charlotte Monday where he’ll speak at the Time Warner Cable Arena on Wednesday. “I’ve been asked to say a few words on Wednesday evening at the start of the convention,” Menino told the Herald today. The mayor said he’s scheduled to speak at 5 p.m. at the convention hall. He’ll also speak at another event being sponsored by the John F. Kennedy Library, he said. The mayor, who is an at-large delegate at the DNC, will be part of a slate of Massachusetts speakers at the convention,...