twoPhaseMixture: return phase names by reference

etc/controlDict

 /*--------------------------------*- C++ -*----------------------------------*\
 | =========                 |                                                 |
 | \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
-|  \\    /   O peration     | Version:  2.0.0                                 |
+|  \\    /   O peration     | Version:  2.3.x                                 |
 |   \\  /    A nd           | Web:      www.OpenFOAM.org                      |
 |    \\/     M anipulation  |                                                 |
 \*---------------------------------------------------------------------------*/
@@ -40,7 +40,7 @@ InfoSwitches
     writeDictionaries 0;
 
     // Allow case-supplied C++ code (#codeStream, codedFixedValue)
-    allowSystemOperations   0;
+    allowSystemOperations   1;
 }
 
 

src/transportModels/twoPhaseMixture/twoPhaseMixture/twoPhaseMixture.H

@@ -2,7 +2,7 @@
   =========                 |
   \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
    \\    /   O peration     |
-    \\  /    A nd           | Copyright (C) 2011-2013 OpenFOAM Foundation
+    \\  /    A nd           | Copyright (C) 2011-2014 OpenFOAM Foundation
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
 License
@@ -78,12 +78,12 @@ public:
 
     // Member Functions
 
-        const word phase1Name() const
+        const word& phase1Name() const
         {
             return phase1Name_;
         }
 
-        const word phase2Name() const
+        const word& phase2Name() const
         {
             return phase2Name_;
         }