cid#1697486: Variable copied when it could be moved

and

cid#1697492: Variable copied when it could be moved
cid#1697489: Variable copied when it could be moved

Change-Id: I8a7027492db6faa7264e0c477d42c84406dbf7be
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/209410
Reviewed-by: Xisco Fauli <xiscofauli@libreoffice.org>
Tested-by: Jenkins

sc/source/solver/SlpSolver.cxx

@@ -610,9 +610,9 @@ void SAL_CALL SLPSolver::solve()
             }
             updateCurvature(aB, aPointChange, aGradientChange);
 
-            aX = aTrial;
-            aGradient = aNewGradient;
-            aCells = aCellsNew;
+            aX = std::move(aTrial);
+            aGradient = std::move(aNewGradient);
+            aCells = std::move(aCellsNew);
             fMerit = fMeritTrial;
 
             double fRatio = fPredicted > fMinPredictedReduction ? fActual / fPredicted : 1.0;