Fix job control on DragonFly BSD

[YONETANI Tomokazu]

Hi,
DragonFly BSD needs the same trick as FreeBSD does in fgtty(),
or else you lose job control inside screen.

Cheers,
YONETANI Tomokazu.

diff --git a/src/tty.sh b/src/tty.sh
index 814f3d9..b691dbf 100644
--- a/src/tty.sh
+++ b/src/tty.sh
@@ -812,7 +812,7 @@ int fd;
   /*
    * Under BSD we have to set the controlling terminal again explicitly.
    */
-# if (defined(__FreeBSD_kernel__) || defined(__GNU__)) && defined(TIOCSCTTY)
+# if (defined(__FreeBSD_kernel__) || defined(__DragonFly__) || 
defined(__GNU__)) && defined(TIOCSCTTY)
   ioctl(fd, TIOCSCTTY, (char *)0);
 # endif