* cygheap.cc (cygheap_root::set): Avoid treating '/' specially.

* fhandler.cc (fhandler_base::fcntl): Only set specific O_NDELAY style flag
passed in from application.
* fhandler_socket.cc (fhandler_socket::fcntl): Ditto.
* fhandler.h: Set constant for future use.
* winsup.h: Define OLD_O_NDELAY only for old programs.
* include/cygwin/version.h: Define CYGWIN_VERSION_CHECK_FOR_OLD_O_NONBLOCK.

winsup/cygwin/cygheap.cc

@@ -330,6 +330,15 @@ cstrdup1 (const char *s)
 void
 cygheap_root::set (const char *posix, const char *native)
 {
+  if (*posix == '/' && posix[1] == '\0')
+    {
+      if (m)
+	{
+	  cfree (m);
+	  m = NULL;
+	}
+      return;
+    }
   if (!m)
     m = (struct cygheap_root_mount_info *) ccalloc (HEAP_MOUNT, 1, sizeof (*m));
   strcpy (m->posix_path, posix);