Cygwin: POSIX msg queues: implement ioctl(2)

Call into fhandler_base::ioctl immediately, thus only allowing
FIONBIO to manipulate blocking behaviour.

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

winsup/cygwin/fhandler.h

@@ -3145,6 +3145,7 @@ public:
 
   int __reg2 fstat (struct stat *buf);
   int dup (fhandler_base *child, int);
+  int ioctl (unsigned int, void *);
   int close ();
 
   void copy_from (fhandler_base *x)

winsup/cygwin/fhandler_mqueue.cc

@@ -411,6 +411,12 @@ fhandler_mqueue::fixup_after_fork (HANDLE parent)
     api_fatal ("Creating IPC object failed in fork, %E");
 }
 
+int
+fhandler_mqueue::ioctl (unsigned int cmd, void *buf)
+{
+  return fhandler_base::ioctl (cmd, buf);
+}
+
 int
 fhandler_mqueue::close ()
 {