Improve threading and i/o routines

- On Windows connect() can now be interrupted by a signal; connect() w/
  O_NONBLOCK will now raise EINPROGRESS; and connect() with SO_SNDTIMEO
  will raise ETIMEDOUT after the interval has elapsed.

- We now get the AcceptEx(), ConnectEx(), and TransmitFile() functions
  from the WIN32 API the officially blessed way, using WSAIoctl().

- Do nothing on Windows when fsync() is called on a directory handle.
  This was raising EACCES earlier becaues GENERIC_WRITE is required on
  the handle. It's possible to FlushFileBuffers() a directory handle if
  it's opened with write access but MSDN doesn't document what it does.
  If you have any idea, please let us know!

- Prefer manual reset event objects for read() and write() on Windows.

- Do some code cleanup on our dlmalloc customizations.

- Fix errno type error in Windows blocking routines.

- Make the futex polyfill simpler and faster.

libc/calls/struct/fd.internal.h

@@ -14,15 +14,17 @@ COSMOPOLITAN_C_START_
 
 struct Fd {
   char kind;
+  bool isbound;
   unsigned flags;
   unsigned mode;
-  int64_t handle;
-  int64_t pointer;
+  long handle;
+  long pointer;
   int family;
   int type;
   int protocol;
-  uint32_t rcvtimeo;
-  uint32_t sndtimeo;
+  unsigned rcvtimeo; /* millis; 0 means wait forever */
+  unsigned sndtimeo; /* millis; 0 means wait forever */
+  void *connect_op;
 };
 
 struct Fds {