[2387] Add includes

These are not strictly necessary, as other headers include <memory>.

src/lib/dns/rdata/generic/dnskey_48.cc

@@ -27,6 +27,8 @@
 #include <dns/rdata.h>
 #include <dns/rdataclass.h>
 
+#include <memory>
+
 #include <stdio.h>
 #include <time.h>
 

src/lib/dns/rdata/generic/nsec3_50.cc

@@ -35,6 +35,8 @@
 #include <dns/rdata/generic/detail/nsec_bitmap.h>
 #include <dns/rdata/generic/detail/nsec3param_common.h>
 
+#include <memory>
+
 #include <stdio.h>
 #include <time.h>
 

src/lib/dns/rdata/generic/nsec3param_51.cc

@@ -22,6 +22,7 @@
 
 #include <boost/lexical_cast.hpp>
 
+#include <memory>
 #include <string>
 #include <sstream>
 #include <vector>