COMP: deprecate domainName and full hostName (#2280)

- unused in regular OpenFOAM code
- POSIX version uses deprecated gethostbyname()
- Windows version never worked

COMP: localize, noexcept on internal OSspecific methods

STYLE: support fileName::Type SYMLINK and LINK as synonyms

applications/utilities/parallelProcessing/redistributePar/loadOrCreateMesh.C

@@ -459,7 +459,7 @@ bool Foam::removeEmptyDir(const fileName& path)
             Foam::readDir
             (
                 path,
-                fileName::LINK,
+                fileName::SYMLINK,
                 false,                  // filterGz
                 false                   // followLink
             )