Filed at 4:21 p.m. ET LOS ANGELES (Reuters) - Rock guitarist Robbin Crosby, a founding member of the 1980s heavy-metal ``hair'' band Ratt, has died after an eight-year battle with AIDS, according to the group's official Web site. He was 42. Crosby, who went public with his illness in a radio interview last July, saying he had contracted the disease through heroin use, died on Thursday. The band's Web site (http://www.therattpack.com) carried a photograph of the guitarist performing in concert beneath the words, ``In Memory of Robbin Crosby.'' The site's ``forum'' section posted dozens of messages of condolences from grieving...