Add support for explicit constructor calls in Microsoft mode.

For example: 

class A{ 
public:
  A& operator=(const A& that) {
      if (this != &that) {
          this->A::~A();
          this->A::A(that);  // <=== explicit constructor call.
      }
      return *this;
  }
};

More work will be needed to support an explicit call to a template constructor.

llvm-svn: 123735