fix a lot of issues on psogc; add proxy module

- $ann implemented
- concurrency removed; server is now single-threaded, event-driven and much more stable
- rare seed is no longer the game id; ids are sequential from server startup so they weren't random at all before
- supports dropping privileges; now you can run it as root so it can open a sockets on low ports, then it will switch to the given user before serving any traffic
- newserv now behaves like a proxy if you run it with the --proxy-destination=<IP_OR_HOSTNAME> argument; there's also an (invisible) shell in this mode where you can inject commands to the server or client. e.g. it can always be christmas in the lobby if you do `sc DA 01 00 00`
- increased the mtu on PSODolphinConfig's tap0 configuration; this seems to make the connection more stable
- fixed some uninitialized memory bugs
- the shell is now event-driven and now uses libevent too; unfortunately this means readline doesn't work anymore (no history and vim-like shortcuts)
- made network command display consistent for input vs. output (the header appears in both cases now)
- fixed bugs in some subcommand handling (the BB logic was being applied to non-BB clients erroneously, causing most item drops not to work at all)
- fixed player tags in the short lobby data struct. unclear if this was actually a problem but it was inconsistent with other servers
- fixed "unused" field in game join command (actually it appears to be disable_udp and should be 1, not 0)
- cleaned up Server abstraction a bit
- rewrote some text functions; asan was complaining about the built-in ones for some reason
- added an optional welcome message

DNSServer.hh

@@ -1,14 +1,17 @@
 #pragma once
 
-#include <atomic>
-#include <thread>
+#include <event2/event.h>
+
+#include <memory>
+#include <unordered_map>
 #include <string>
 #include <set>
 
 
 class DNSServer {
 public:
-  DNSServer(uint32_t local_connect_address, uint32_t external_connect_address);
+  DNSServer(std::shared_ptr<struct event_base> base,
+      uint32_t local_connect_address, uint32_t external_connect_address);
   DNSServer(const DNSServer&) = delete;
   DNSServer(DNSServer&&) = delete;
   virtual ~DNSServer();
@@ -18,20 +21,13 @@ public:
   void listen(int port);
   void add_socket(int fd);
 
-  virtual void start();
-  virtual void schedule_stop();
-  virtual void wait_for_stop();
-
 private:
-  std::atomic<bool> should_exit;
-  std::thread t;
-
-  std::set<int> fds;
-
+  std::shared_ptr<struct event_base> base;
+  std::unordered_map<int, std::unique_ptr<struct event, void(*)(struct event*)>> fd_to_receive_event;
   uint32_t local_connect_address;
   uint32_t external_connect_address;
 
-  void run_thread();
-  static std::string build_response(const std::string& input,
-      uint32_t connect_address);
+  static void dispatch_on_receive_message(evutil_socket_t fd, short events,
+      void* ctx);
+  void on_receive_message(int fd, short event);
 };