minor cleanup for reverted string changes (commit 4f5f66e7)

- put back debug switch (even although it is never used)
- remove stringsGlobals.C, since it is now never used

etc/controlDict

@@ -687,6 +687,7 @@ DebugSwitches
     staticFvMesh        0;
     steadyState         0;
     stl                 0;
+    string              0;
     stochasticDispersionRAS 0;
     supersonicFreestream 0;
     surfaceFeatures     0;

src/OpenFOAM/primitives/strings/stringsGlobals.C

-/*---------------------------------------------------------------------------*\
-  =========                 |
-  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
-   \\    /   O peration     |
-    \\  /    A nd           | Copyright (C) 1991-2009 OpenCFD Ltd.
-     \\/     M anipulation  |
--------------------------------------------------------------------------------
-License
-    This file is part of OpenFOAM.
-
-    OpenFOAM is free software; you can redistribute it and/or modify it
-    under the terms of the GNU General Public License as published by the
-    Free Software Foundation; either version 2 of the License, or (at your
-    option) any later version.
-
-    OpenFOAM is distributed in the hope that it will be useful, but WITHOUT
-    ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
-    FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
-    for more details.
-
-    You should have received a copy of the GNU General Public License
-    along with OpenFOAM; if not, write to the Free Software Foundation,
-    Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
-
-Description
-    Static initializers for
-        Foam::string::null
-        Foam::word::null
-        Foam::fileName::null.
-    This file is included in global.Cver since these members are required by
-    debug.C.
-
-\*---------------------------------------------------------------------------*/
-
-#include "string.H"
-#include "word.H"
-#include "fileName.H"
-
-// * * * * * * * * * * * * * * Static Data Members * * * * * * * * * * * * * //
-
-// ************************************************************************* //