AbbVie struck a deal to buy Botox-maker, and the biggest name in medical aesthetics, Allergan, for roughly $63 billion. It’s doing so to diversify a portfolio that includes the world’s best-selling drug, Humira, which will soon face generic competition in Europe.   The combined company will consist of several franchises with leadership positions across immunology, hematologic oncology, medical aesthetics, neuroscience, women’s health, eye care and virology.   “This is a transformatio...