ENH: suppress Info output for some cases (issue #722, #893)

- add additional control via a Foam::infoDetailLevel flag, which is
  supported by a 'DetailLevel' macro.  Eg,

      DetailLevel << "some information" << nl

- When infoDetailLevel is zero, the stdout for all Foam::system() calls
  are also redirected to stderr to prevent child output from
  appearing on the parent.

- close stdin before exec in system call.

src/OpenFOAM/db/dynamicLibrary/codedBase/codedBase.C

@@ -3,7 +3,7 @@
   \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
    \\    /   O peration     |
     \\  /    A nd           | Copyright (C) 2011-2016 OpenFOAM Foundation
-     \\/     M anipulation  | Copyright (C) 2016 OpenCFD Ltd.
+     \\/     M anipulation  | Copyright (C) 2016-2018 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -350,7 +350,8 @@ void Foam::codedBase::updateLibrary
         return;
     }
 
-    Info<< "Using dynamicCode for " << this->description().c_str()
+    DetailInfo
+        << "Using dynamicCode for " << this->description().c_str()
         << " at line " << dict.startLineNumber()
         << " in " << dict.name() << endl;