unix: add ioctl functions on Darwin

Add IoctlGetInt/IoctlSetInt, IoctlGetTermios/IoctlSetTermios and
IoctlGetWinsize/IoctlSetWinsize on Darwin. These are similar to the
already existing implementations on Linux and Solaris.

Generated on Mac OS 10.11 (Darwin 15.6.0).

Change-Id: I2d4cc957c840836fcc2ccb71c67631420f4a2eb1
Reviewed-on: https://go-review.googlesource.com/52410
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
diff --git a/unix/ztypes_darwin_arm64.go b/unix/ztypes_darwin_arm64.go
index 85d56ea..8756d04 100644
--- a/unix/ztypes_darwin_arm64.go
+++ b/unix/ztypes_darwin_arm64.go
@@ -455,3 +455,10 @@
 	Ispeed    uint64
 	Ospeed    uint64
 }
+
+type Winsize struct {
+	Row    uint16
+	Col    uint16
+	Xpixel uint16
+	Ypixel uint16
+}