[3970] Added missing includes in WatchSocket.

src/lib/util/watch_socket.cc

@@ -19,6 +19,7 @@
 
 #include <fcntl.h>
 #include <errno.h>
+#include <string.h>
 #include <sys/select.h>
 
 namespace isc {

src/lib/util/watch_socket.h

@@ -22,6 +22,7 @@
 #include <boost/shared_ptr.hpp>
 
 #include <stdint.h>
+#include <string>
 
 namespace isc {
 namespace util {