LimitedScheme/LimitFuncs: Make the limiter function for symmTensor consistent with tensor

Use the trace as the limiter function for both symmTensor and tensor to
bound the normal stresses rather than the shear stresses.

Resolves bug-report http://www.openfoam.org/mantisbt/view.php?id=1751

src/finiteVolume/interpolation/surfaceInterpolation/limitedSchemes/LimitedScheme/LimitFuncs.C

@@ -2,7 +2,7 @@
   =========                 |
   \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
    \\    /   O peration     |
-    \\  /    A nd           | Copyright (C) 2011 OpenFOAM Foundation
+    \\  /    A nd           | Copyright (C) 2011-2015 OpenFOAM Foundation
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
 License
@@ -55,6 +55,16 @@ inline tmp<volScalarField> magSqr<scalar>::operator()
 }
 
 
+template<>
+inline tmp<volScalarField> magSqr<symmTensor>::operator()
+(
+    const volSymmTensorField& phi
+) const
+{
+    return Foam::tr(phi);
+}
+
+
 template<>
 inline tmp<volScalarField> magSqr<tensor>::operator()
 (