pdns: fix compilation with boost 1.73

Signed-off-by: Rosen Penev <rosenp@gmail.com>

net/pdns/patches/300-boost-173.patch

@@ -0,0 +1,32 @@
+--- a/pdns/ixfrdist-web.cc
++++ b/pdns/ixfrdist-web.cc
+@@ -25,6 +25,8 @@
+ #include "iputils.hh"
+ #include "ixfrdist-stats.hh"
+ 
++using namespace boost::placeholders;
++
+ string doGetStats();
+ 
+ IXFRDistWebServer::IXFRDistWebServer(const ComboAddress &listenAddress, const NetmaskGroup &acl, const string &loglevel) :
+--- a/pdns/webserver.cc
++++ b/pdns/webserver.cc
+@@ -36,6 +36,8 @@
+ #include "uuid-utils.hh"
+ #include <yahttp/router.hpp>
+ 
++using namespace boost::placeholders;
++
+ json11::Json HttpRequest::json()
+ {
+   string err;
+--- a/pdns/ws-auth.cc
++++ b/pdns/ws-auth.cc
+@@ -49,6 +49,7 @@
+ #include "tsigutils.hh"
+ 
+ using json11::Json;
++using namespace boost::placeholders;
+ 
+ extern StatBag S;
+