FStream: Remove unused basic_filebuf declaration.

This fixes compile errors on older compilers where basic_filebuf is
not available.

Change-Id: If220925774b5d31b128065603cf365a7a5ec5f42

FStream.hxx.in

@@ -161,7 +161,6 @@ class basic_ofstream : public std::basic_ostream<CharType,Traits>
   typedef basic_ofstream<char> ofstream;
 
 #else
-  using @KWSYS_NAMESPACE@_ios_namespace::basic_filebuf;
   using @KWSYS_NAMESPACE@_ios_namespace::ofstream;
   using @KWSYS_NAMESPACE@_ios_namespace::ifstream;
 #endif