Provide a new traits class remove_const which is identical to the current

RemoveConst (except that the return type is now 'type' instead of 'Type').
If the tr1/type_traits header is present, remove_const will be taken from
there.  If not, remove_const is a copy of the RemoveConst class in this
file.

[[Imported from SVN: r4844]]

common/typetraits.hh

@@ -5,6 +5,10 @@
 
 #include <dune/common/logictraits.hh>
 
+#ifdef HAVE_TR1_TYPE_TRAITS
+#include <tr1/type_traits>
+#endif
+
 namespace Dune
 {
 
@@ -161,6 +165,19 @@ namespace Dune
     typedef typename RemoveConstHelper<T, IsVolatile<T>::value>::Type Type;
   };
 
+#ifdef HAVE_TR1_TYPE_TRAITS
+  using std::tr1::remove_const;
+#else
+  /**
+   * @brief Removes a const qualifier while preserving others.
+   */
+  template<typename T>
+  struct remove_const
+  {
+    typedef typename RemoveConstHelper<T, IsVolatile<T>::value>::Type type;
+  };
+#endif
+
   /**
    * @brief Checks wether a type is derived from another.
    *