ENH: portable scoping char for solver info names (#2224, #1675)

COMP: implicit cast scope name to C++-string in IOobject::scopedName

- handles 'const char*' and allows a check for an empty scope name

COMP: avoid potential name conflict in local function (Istream)

- reportedly some resolution issues (unconfirmed) with Fujitsu clang

src/functionObjects/utilities/solverInfo/solverInfo.C

@@ -86,7 +86,10 @@ void Foam::functionObjects::solverInfo::createResidualField
         return;
     }
 
-    const word residualName("initialResidual:" + fieldName);
+    const word residualName
+    (
+        IOobject::scopedName("initialResidual", fieldName)
+    );
 
     if (!mesh_.foundObject<IOField<scalar>>(residualName))
     {