Merge branch 'qss-solver-dev' into release-6.1.1

Author: joaquinffernandez

src/engine/tests/system/gt_data/acousticsRiemDes/acousticsRiemDes.mo

@@ -38,7 +38,7 @@ equation
 		MMO_SymDiff=false,
 		MMO_PartitionMethod=Metis,
 		MMO_Output={p[1:N/5:N]},
-		Jacobian=Sparse,
+		Jacobian=Dense,
 		MMO_BDF_PDepth=1,
 		MMO_BDF_Max_Step=0,
 		StartTime=0.0,

src/engine/tests/system/gt_data/adr2D/adr2D.mo

@@ -30,7 +30,7 @@ end for;
 		MMO_DT_Synch=SD_DT_Fixed,
 		MMO_DT_Min=1e-3,
 		MMO_Output={u[2,2]},
-		Jacobian=Sparse,
+		Jacobian=Dense,
 		MMO_BDF_PDepth=1,
 		MMO_BDF_Max_Step=0,
 		StartTime=0.0,