Make MultiDimFit::GridType public

This fixes compilation with more pedantinc compilers: even though the
`RandStartPtr` was declared as a friend class, it uses the
`MultiDimFit::GridType` in its public interface. This is not allowed.

interface/MultiDimFit.h

@@ -23,15 +23,14 @@ class MultiDimFit : public FitterAlgoBase {
   }
   virtual void applyOptions(const boost::program_options::variables_map &vm) ;
 
-  friend class RandStartPt;
+  enum GridType { G1x1, G3x3 };
 
 protected:
   virtual bool runSpecific(RooWorkspace *w, RooStats::ModelConfig *mc_s, RooStats::ModelConfig *mc_b, RooAbsData &data, double &limit, double &limitErr, const double *hint);
 
   enum Algo { None, Singles, Cross, Grid, RandomPoints, Contour2D, Stitch2D, FixedPoint, Impact };
   static Algo algo_;
 
-  enum GridType { G1x1, G3x3 };
   static GridType gridType_;
 
   static std::vector<std::string>  poi_;