One of Canada's greatest journalists shares a half century of the stories behind the stories.From his vantage point harnessed to a tree overlooking the town of Huntsville (he tended to wander), a very young Roy MacGregor got in the habit of watching people—what they did, who they talked to, where they went. He has been getting to know his fellow Canadians and telling us all about them ever since.    From his early days in the pages of Maclean's, to stints at the Toronto Star,