Add empty serialization func for std::less

-Resolves issues with compiling priority_queue (#264)
-Removed std::less serialization from testing common file

include/cereal/types/functional.hpp

@@ -0,0 +1,44 @@
+/*! \file functional.hpp
+    \brief Support for types found in \<functional\>
+    \ingroup STLSupport */
+/*
+  Copyright (c) 2014, Randolph Voorhies, Shane Grant
+  All rights reserved.
+
+  Redistribution and use in source and binary forms, with or without
+  modification, are permitted provided that the following conditions are met:
+      * Redistributions of source code must retain the above copyright
+        notice, this list of conditions and the following disclaimer.
+      * Redistributions in binary form must reproduce the above copyright
+        notice, this list of conditions and the following disclaimer in the
+        documentation and/or other materials provided with the distribution.
+      * Neither the name of cereal nor the
+        names of its contributors may be used to endorse or promote products
+        derived from this software without specific prior written permission.
+
+  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+  ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+  WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+  DISCLAIMED. IN NO EVENT SHALL RANDOLPH VOORHIES OR SHANE GRANT BE LIABLE FOR ANY
+  DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+  (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+  LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+  ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+  (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+  SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+*/
+#ifndef CEREAL_TYPES_FUNCTIONAL_HPP_
+#define CEREAL_TYPES_FUNCTIONAL_HPP_
+
+#include <cereal/details/helpers.hpp>
+#include <functional>
+
+namespace cereal
+{
+  //! Saving for std::less
+  template <class Archive, class T> inline
+  void serialize( Archive &, std::less<T> & )
+  { }
+} // namespace cereal
+
+#endif // CEREAL_TYPES_FUNCTIONAL_HPP_

include/cereal/types/queue.hpp

@@ -35,6 +35,8 @@
 
 // The default container for queue is deque, so let's include that too
 #include <cereal/types/deque.hpp>
+// The default comparator for queue is less
+#include <cereal/types/functional.hpp>
 
 namespace cereal
 {

unittests/common.hpp

@@ -90,13 +90,6 @@ namespace boost
   }
 }
 
-namespace cereal
-{
-  template <class Archive, class T> inline
-    void serialize( Archive &, std::less<T> & )
-    { }
-}
-
 template<class T> inline
 typename std::enable_if<std::is_floating_point<T>::value, T>::type
 random_value(std::mt19937 & gen)