CXX-253 Include-what-you-use for make_shared

Older boost doesn't include make_shared.hpp in smart_ptr.hpp, so the
include of smart_ptr.hpp in pch.h doesn't make make_shared.hpp available
in the replica_set_monitor files.

Author: acmorrow

src/mongo/client/replica_set_monitor.cpp

@@ -16,6 +16,7 @@
 #include "mongo/client/replica_set_monitor.h"
 
 #include <algorithm>
+#include <boost/make_shared.hpp>
 #include <boost/thread.hpp>
 #include <limits>
 

src/mongo/client/replica_set_monitor_test.cpp

@@ -13,6 +13,8 @@
  *    limitations under the License.
  */
 
+#include <boost/make_shared.hpp>
+
 #include "mongo/client/connpool.h"
 #include "mongo/client/dbclientinterface.h"
 #include "mongo/client/dbclient_rs.h"