ENH: also accept reading fileName as wordToken

- should have been part of commit 9d36d3c0
  which allows us to upcast a word to a fileName.

src/OpenFOAM/primitives/strings/fileName/fileNameIO.C

@@ -2,7 +2,7 @@
   =========                 |
   \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
    \\    /   O peration     |
-    \\  /    A nd           | Copyright (C) 2018 OpenCFD Ltd.
+    \\  /    A nd           | Copyright (C) 2018-2019 OpenCFD Ltd.
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
                             | Copyright (C) 2011-2017 OpenFOAM Foundation
@@ -51,8 +51,9 @@ Foam::Istream& Foam::operator>>(Istream& is, fileName& val)
         return is;
     }
 
-    if (t.isString())
+    if (t.isStringType())
     {
+        // Also accept a plain word as a fileName
         val = t.stringToken();
     }
     else