Return unique inode numbers when calling stat/fstat on pipes and IP sockets

* fhandler.h (class fhandler_base): Convert unique_id to int64_t.
        (fhandler_base::set_ino): New protected inline method.
        (fhandler_base::get_unique_id): Convert to int64_t.
        (fhandler_base::set_unique_id): New inline method taking int64_t.
        (fhandler_pipe::fstat): Declare.
        (fhandler_pipe::init): Take extra parameter.
        (fhandler_pipe::create): Ditto.
        * fhandler_socket.cc (fhandler_socket::init_events): Set inode number
        to serial number.
        (fhandler_socket::fstat): Set device to DEV_TCP_MAJOR.  Create st_ino
        from get_ino.
        * include/cygwin/signal.h (struct _sigcommune): Replace
        _si_pipe_fhandler with _si_pipe_unique_id.
        * pinfo.h (_pinfo::pipe_fhandler): Take unique id instead of HANDLE.
        * pinfo.cc (commune_process): Accommodate change to _si_pipe_unique_id.
        (_pinfo::commune_request): Ditto.
        (_pinfo::pipe_fhandler): Ditto.
        * pipe.cc (fhandler_pipe::init): Take unique id as argument and set
        inode number and unique_id from there.
        (fhandler_pipe::open): Rework to find any matching pipe from unique
        id in filename.
        (fhandler_pipe::get_proc_fd_name): Create filename using inode number.
        (fhandler_pipe::create): Generate and return unique id from process pid
        and pipe_unique_id.  In outer method, call init with additional unique
        id as parameter.
        (fhandler_pipe::fstat): New method.
        (pipe_worker): Accommodate using 64 bit inode number in filename.

Signed-off-by: Corinna Vinschen <corinna@vinschen.de>

winsup/cygwin/include/cygwin/signal.h

@@ -188,7 +188,7 @@ struct _sigcommune
   __extension__ union
   {
     int _si_fd;
-    void *_si_pipe_fhandler;
+    int64_t _si_pipe_unique_id;
     char *_si_str;
   };
 };