Having Shaquille O’Neal, one of the greatest basketball players of all time, as an investor, alongside a sterling roster of Irish tech backers, adds a special cachet to Limbo, the new weight-loss venture with its origins in Cork.  The start-up, which has announced a $6 million seed raise today and is co-founded by the Cork entrepreneur Pat Phelan, has been working in the background for two years in preparation for its launch. It is initially targeting the Irish and UK markets, but the plan is to quickly follow it up with a global push.  Phelan credits a prototyped version of…