Give up with --std=c++11

There are too many distros that use old versions of g++ that don't support it adequately.

unit-tests/cache_t.cc

@@ -19,6 +19,8 @@
 #include "gmock/gmock.h"
 #include "persistent-data/cache.h"
 
+#include <boost/shared_ptr.hpp>
+
 using namespace boost;
 using namespace base;
 using namespace std;
@@ -53,7 +55,7 @@ namespace {
 
 	struct SharedThingTraits {
 		typedef unsigned key_type;
-		typedef std::shared_ptr<Thing> value_type;
+		typedef boost::shared_ptr<Thing> value_type;
 
 		static key_type get_key(value_type const &p) {
 			return p->key_;