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

FileContentsCache.cc

@@ -15,24 +15,18 @@ shared_ptr<const string> FileContentsCache::get(const std::string& name) {
 
   uint64_t t = now();
   try {
-    lock_guard<mutex> g(this->lock);
     auto& entry = this->name_to_file.at(name);
     if (t - entry.load_time < 300000000) { // not 5 minutes old? return it
       return entry.contents;
     }
   } catch (const out_of_range& e) { }
 
-    shared_ptr<const string> contents(new string(load_file(name)));
-
-    {
-      lock_guard<mutex> g(this->lock);
-      this->name_to_file.erase(name);
-      this->name_to_file.emplace(piecewise_construct, forward_as_tuple(name),
-          forward_as_tuple(name, contents, t));
-    }
-
-    return contents;
+  shared_ptr<const string> contents(new string(load_file(name)));
+  this->name_to_file.erase(name);
+  this->name_to_file.emplace(piecewise_construct, forward_as_tuple(name),
+      forward_as_tuple(name, contents, t));
 
+  return contents;
 }
 
 shared_ptr<const string> FileContentsCache::get(const char* name) {