ENH: make treatment of stream allocators more uniform (issue #532)

- use allocator class to wrap the stream pointers instead of passing
  them into ISstream, OSstream and using a dynamic cast to delete
  then. This is especially important if we will have a bidirectional
  stream (can't delete twice!).

STYLE:

- file stream constructors with std::string (C++11)

- for rewind, explicit about in|out direction. This is not currently
  important, but avoids surprises with any future bidirectional access.

- combined string streams in StringStream.H header.
  Similar to <sstream> include that has both input and output string
  streams.

src/fileFormats/ensight/read/ensightReadFile.C

@@ -24,7 +24,6 @@ License
 \*---------------------------------------------------------------------------*/
 
 #include "ensightReadFile.H"
-#include <sstream>
 
 // * * * * * * * * * * * * * * * * Constructors  * * * * * * * * * * * * * * //
 

src/fileFormats/nas/NASCore.C

@@ -24,7 +24,7 @@ License
 \*---------------------------------------------------------------------------*/
 
 #include "NASCore.H"
-#include "IStringStream.H"
+#include "StringStream.H"
 
 // * * * * * * * * * * * * * * * * Constructors  * * * * * * * * * * * * * * //
 

src/fileFormats/starcd/STARCDCore.C

@@ -27,7 +27,7 @@ License
 #include "ListOps.H"
 #include "clock.H"
 #include "PackedBoolList.H"
-#include "IStringStream.H"
+#include "StringStream.H"
 #include "OSspecific.H"
 
 

src/fileFormats/stl/STLCore.C

@@ -89,9 +89,9 @@ int Foam::fileFormats::STLCore::detectBinaryHeader
 )
 {
     bool compressed = false;
-    autoPtr<istream> streamPtr
+    autoPtr<std::istream> streamPtr
     (
-        new ifstream(filename.c_str(), std::ios::binary)
+        new std::ifstream(filename, std::ios::binary)
     );
 
     // If the file is compressed, decompress it before further checking.
@@ -100,7 +100,7 @@ int Foam::fileFormats::STLCore::detectBinaryHeader
         compressed = true;
         streamPtr.reset(new igzstream((filename + ".gz").c_str()));
     }
-    istream& is = streamPtr();
+    std::istream& is = streamPtr();
 
     if (!is.good())
     {
@@ -165,9 +165,9 @@ Foam::fileFormats::STLCore::readBinaryHeader
     bool compressed = false;
     nTrisEstimated = 0;
 
-    autoPtr<istream> streamPtr
+    autoPtr<std::istream> streamPtr
     (
-        new ifstream(filename.c_str(), std::ios::binary)
+        new std::ifstream(filename, std::ios::binary)
     );
 
     // If the file is compressed, decompress it before reading.
@@ -176,7 +176,7 @@ Foam::fileFormats::STLCore::readBinaryHeader
         compressed = true;
         streamPtr.reset(new igzstream((filename + ".gz").c_str()));
     }
-    istream& is = streamPtr();
+    std::istream& is = streamPtr();
 
     if (!is.good())
     {