LONDON (Reuters) - George Michael is writing a song about his near-death battle with illness in a Vienna hospital last year, the British singer announced on Twitter on Wednesday. Michael, 48, was diagnosed with severe pneumonia in November and treated in the Austrian capital where he was taken ill. He was forced to postpone his tour and spent several weeks in hospital, describing his illness as "touch and go". On his Twitter feed, he wrote: "I've been a busy boy in the studio this week ... finally ready to write about what happened to me in Vienna ... ...