Fix numerous thread/socket lifecycle crashes and TLS/epoll write-stall busy-loop

Thread/EPoll lifecycle:
- Thread::~Thread() now actually joins/frees its worker thread (was
  empty - the OS thread kept running against already-freed EPoll/Socket
  objects on any early teardown, a confirmed "double free" crash)
- EPoll::~EPoll() calls stop() if never explicitly stopped, for the
  same reason
- epoll_wait() now uses a 1s timeout instead of blocking forever, so a
  worker thread can actually notice isStopping() and let itself be
  joined
- EPoll::processCommand() iterated threads by value, silently
  double-freeing the real vector's Thread the moment each copy went
  out of scope
- ThreadScope gained onThreadStart()/onThreadEnd() hooks (actually
  wired up now - the constructor that was supposed to store the scope
  discarded it) for per-thread C-library init (e.g. MySQL client)

Socket/TCPSocket/TLS:
- Socket::writeSocket(): give up and shut down a connection after 50
  consecutive zero-progress sends instead of retrying forever -
  SSL_ERROR_WANT_READ on a write needs a READ to make progress, but
  resetSocket() re-arms EPOLLWRNORM regardless, which an
  already-writable TCP socket satisfies immediately - a real stuck
  connection generated 55GB, then 12.9GB of debug log this way before
  being caught
- Socket::writeSocket() now honors sendData()'s actual return value
  (previously discarded, entry popped unconditionally after one call) -
  a large response could get silently truncated past what fit in one
  write()/SSL_write() call
- TLS::registerSocket()/sendData()/receiveData(): `initialized` now
  only goes true once SSL_set_fd() has actually succeeded, and
  sendData()/receiveData() check it first - fixes a real SIGSEGV where
  a new session's own queued greeting could reach SSL_write() on a
  different epoll thread before this session's handshake setup had run
- TCPServer::connectionRequest() now performs the TLS handshake ON THE
  ACCEPTED SESSION, not the listening server itself (was building SSL
  state on the wrong object, leaving every session's own `ssl`
  uninitialized)
- TCPServer::receiveData() always uses the plain (non-TLS) read path -
  the listening socket is never itself a TLS peer
- TCPSocket's block-mode literal reading used an unset `blockLength`
  field instead of `blockSize`, and could busy-spin forever on a
  multi-packet literal
- TCPSocket line scanning replaced an unbounded strcspn() (assumes a
  NUL-terminated buffer; read past a non-NUL-terminated receive buffer
  into adjacent heap memory) with a bounds-checked memchr() scan

Protocol/session handling:
- CommandList::processRequest() now case-folds the command keyword
  before lookup - SMTP/POP3/IMAP commands are spec-required to be
  case-insensitive; a client sending "Mail From:" instead of
  "MAIL FROM:" previously failed to dispatch at all
- TCPSession::protocol() no longer drops blank lines while a handler
  has grabbed input (e.g. __SMTP_DATA reading a message body, an IMAP
  APPEND literal) - those handlers depend on seeing blank lines as
  real content, not commands; this silently corrupted any message body
  containing a blank line
- TCPSession's uuid alias fixed: streaming a raw uuid_t via operator<<
  triggered libstdc++'s unsigned-char* overload (strlen() on 16 binary
  bytes, a real stack-buffer-overflow read), and `alias` pointed at a
  stack-local that was already destroyed by the time the constructor
  returned
- INotify::processEvent() only treats event->name as a NUL-terminated
  string when event->len > 0 (per inotify(7)) instead of unconditional
  strlen() on a field the kernel doesn't guarantee is even present -
  a confirmed heap-buffer-overflow read that had been misdiagnosed as
  a MySQL thread-safety issue

INotify.cpp

@@ -28,32 +28,53 @@ namespace core {
 	   ptr < buffer.getData() + buffer.getLength();
 	   ptr += sizeof(struct inotify_event) + event->len) {
 	 event = (const struct inotify_event *) ptr;
-	 coreutils::ZString name(event->name);
+
+	 // event->name only exists - and is only NUL-terminated - when
+	 // event->len > 0 (inotify(7): "This field is present only when
+	 // the event relates to a file inside a watched directory ...
+	 // otherwise ... this field is absent."). For events with
+	 // len == 0 (e.g. IN_UNMOUNT, IN_Q_OVERFLOW, IN_IGNORED, or
+	 // self-watch events), event->name is not a valid C-string at
+	 // all - calling strlen() on it (as the old ZString(const char*)
+	 // one-arg constructor did unconditionally here) reads past
+	 // whatever garbage follows in the socket's 4096-byte receive
+	 // buffer looking for a NUL, a real heap-buffer-overflow read
+	 // confirmed via AddressSanitizer under concurrent load (the
+	 // eventual heap corruption this caused was previously
+	 // misdiagnosed as a MySQL client thread-safety issue, since it
+	 // surfaces on whichever EPoll worker thread happens to service
+	 // this watcher's socket and corrupts unrelated heap state).
+	 // strnlen() bounded by event->len (rather than the one-arg
+	 // ZString ctor's unbounded strlen) matches the kernel's actual
+	 // guarantee: name is NUL-padded to exactly event->len bytes.
+	 coreutils::ZString name = event->len > 0
+	   ? coreutils::ZString(event->name, strnlen(event->name, event->len))
+	   : coreutils::ZString("");
 
 	 if(event->mask & IN_ACCESS)
 	   inAccess(name);
 	 if(event->mask & IN_ATTRIB)
-	   inAttrib(std::string(event->name));
+	   inAttrib(name.str());
 	 if(event->mask & IN_CLOSE_WRITE)
-	   inCloseWrite(std::string(event->name));
+	   inCloseWrite(name.str());
 	 if(event->mask & IN_CLOSE_NOWRITE)
-	   inCloseNoWrite(std::string(event->name));
+	   inCloseNoWrite(name.str());
 	 if(event->mask & IN_CREATE)
 	   inCreate(name);
 	 if(event->mask & IN_DELETE)
-	   inDelete(std::string(event->name));
+	   inDelete(name.str());
 	 if(event->mask & IN_DELETE_SELF)
-	   inDeleteSelf(std::string(event->name));
+	   inDeleteSelf(name.str());
 	 if(event->mask & IN_MODIFY)
-	   inModify(std::string(event->name));
+	   inModify(name.str());
 	 if(event->mask & IN_MOVE_SELF)
-	   inMoveSelf(std::string(event->name));
+	   inMoveSelf(name.str());
 	 if(event->mask & IN_MOVED_FROM)
-	   inMovedFrom(std::string(event->name));
+	   inMovedFrom(name.str());
 	 if(event->mask & IN_MOVED_TO)
-	   inMovedTo(std::string(event->name));
+	   inMovedTo(name.str());
 	 if(event->mask & IN_OPEN)
-	   inOpen(std::string(event->name));
+	   inOpen(name.str());
       }
    }