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

Thread.cpp

@@ -4,10 +4,35 @@
 
 namespace core {
 
-   Thread::Thread(EPoll &ePoll) : ePoll(ePoll) {}
-   Thread::Thread(EPoll &ePoll, ThreadScope *scope) : ePoll(ePoll) {}
+   Thread::Thread(EPoll &ePoll) : ePoll(ePoll), _thread(NULL), thread(NULL) {}
+   // Previously discarded `scope` entirely (never assigned to the `thread`
+   // member) - a real, live bug found while adding the first actual caller
+   // of this constructor (APIServer's MysqlThreadScope): the whole point
+   // of passing a scope in was to have it invoked from run() below, which
+   // silently never happened.
+   Thread::Thread(EPoll &ePoll, ThreadScope *scope) : ePoll(ePoll), _thread(NULL), thread(scope) {}
 
-   Thread::~Thread() {}
+   // Was empty - _thread (heap-allocated in start()) was never joined or
+   // freed here. A joinable std::thread destroyed without join()/detach()
+   // calls std::terminate() immediately, which this leaked-pointer
+   // approach silently sidestepped: the wrapped OS thread just kept
+   // running - polling this Thread's EPoll reference, touching Socket
+   // objects registered with it - even after this object, its EPoll, and
+   // every one of those sockets had already been destroyed out from under
+   // it (confirmed live: an exception thrown during BARANTMail startup,
+   // after EPoll::start() had already spun up its worker pool, unwound
+   // the stack destructing EPoll and its registered sockets while those
+   // still-running threads kept dereferencing them, producing a real
+   // "double free or corruption" crash). join() first (skipped if already
+   // joined via EPoll::stop() having run normally) so the OS thread is
+   // actually gone before anything it might touch gets freed.
+   Thread::~Thread() {
+      if (_thread) {
+         if (_thread->joinable())
+           _thread->join();
+         delete _thread;
+      }
+   }
 
    void Thread::start() {
       _thread = new std::thread(&Thread::run, this);
@@ -36,11 +61,14 @@ namespace core {
    }
 
    void Thread::run() {
-      
+
       threadId = syscall(SYS_gettid);
-      
+
       coreutils::Log(coreutils::LOG_DEBUG_1) << "Thread started with thread id " << threadId << ".";
-      
+
+      if(thread)
+	thread->onThreadStart();
+
       count = 0;
       
       struct epoll_event events[50];
@@ -50,14 +78,25 @@ namespace core {
 	 if(ePoll.isStopping())
            break;
 	 
-	 status = "WAITING";
-	 int rc = epoll_wait(ePoll.getDescriptor(), events, 50, -1);
-	 status = "RUNNING";
-	 
-	 if(rc < 0) {
-	    // TODO: Make log entry indicating status received and ignore for now.
-	 } else if(rc == 0) {
-	    break;
+		 status = "WAITING";
+		 // A finite timeout, not the previous -1 (wait forever), is what
+		 // makes EPoll::stop() able to return at all: a thread idly
+		 // blocked here with no socket activity would otherwise never
+		 // re-check isStopping() above, so join()ing it (both
+		 // EPoll::stop() and, now, ~Thread() itself) would hang forever.
+		 // Costs up to a one-second shutdown latency.
+		 int rc = epoll_wait(ePoll.getDescriptor(), events, 50, 1000);
+		 status = "RUNNING";
+
+		 if(rc < 0) {
+		    // TODO: Make log entry indicating status received and ignore for now.
+		 } else if(rc == 0) {
+		    // Plain timeout, no socket activity - not itself a signal to
+		    // stop (isStopping() above already decides that). Previously
+		    // broke out of the loop unconditionally, which the old
+		    // infinite wait never actually triggered in practice, but
+		    // would have silently ended this thread after any single
+		    // idle second once the wait became finite.
 	 } else if(rc > 0) {
 	    for(int ix = 0; ix < rc; ++ix) {
 	       ++count;
@@ -72,6 +111,10 @@ namespace core {
             }
 	 }
       }
+
+      if(thread)
+	thread->onThreadEnd();
+
       coreutils::Log(coreutils::LOG_DEBUG_1) << "Thread ending with thread id " << threadId << ".";
    }