`ReachingDefinitionsPass`: free loads are definers

In our reaching definition analysis we used to consider all the loads
not reached by any store as definitions. However we forgot to actually
register them as such, with the result that two consecutive loads from
the same CSV would end up being two free loads.

reachingdefinitions.cpp

@@ -1155,6 +1155,7 @@ bool ReachingDefinitionsImplPass<BBI, R>::runOnFunction(Function &F) {
               Instruction *I = P.first;
               return isa<LoadInst>(I) && MemoryAccess(I, TSP) == TargetMA;
             });
+          Definitions.push_back({ Load, TargetMA });
 
         } else {