Fix sorting criterion in particle map, to make results reproducible (merge -c19516 from trunk)

CSSHOWER++/Main/CS_Shower.C

@@ -366,7 +366,7 @@ bool CS_Shower::PrepareShowerFromSoft(Cluster_Amplitude *const ampl)
   p_ms    = ampl->MS();
   p_next->clear();
   //msg_Tracking()<<*ampl<<"\n";
-  std::map<Parton*,Cluster_Leg*> lmap;
+  std::map<Parton*,Cluster_Leg*,partcomp> lmap;
   std::map<Cluster_Leg*,Parton*> pmap;
 
   Parton      * parton;

CSSHOWER++/Main/CS_Shower.H

@@ -8,6 +8,16 @@
 
 namespace CSSHOWER {
 
+
+  struct partcomp{
+    bool operator() (const Parton * part1, const Parton * part2) const
+    {
+      if (part1->Id() < part2->Id()) return true;
+      else return false;
+    }
+  };
+
+
   class Splitting_Function_Base;
 
   typedef std::map<size_t,std::pair<double,double> > KT2X_Map;