Merge pull request #3877 from rgacogne/dnsdist-max-fds

dnsdist: Increase max FDs in systemd unit, warn if clearly too low

diff --cc pdns/dnsdist.cc
index 459dc36991cbab476cfed2d15daa59cf2e7dc640,5ffe708f949e0ae8f466eb4914db7fd94e6e8c38..1035b6bebbf5ebff7b86e8c1b919817e36dcf342
--- 1/pdns/dnsdist.cc
--- 2/pdns/dnsdist.cc
+++ b/pdns/dnsdist.cc
@@@ -40,8 -40,8 +40,9 @@@
  #include <pwd.h>
  #include "lock.hh"
  #include <getopt.h>
+ #include <sys/resource.h>
  #include "dnsdist-cache.hh"
 +#include "gettime.hh"
  
  #ifdef HAVE_SYSTEMD
  #include <systemd/sd-daemon.h>