unix: add ioctl functions on OpenBSD

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

Change-Id: I99e9434fa50338a0b5d825490513e9383539727d
Reviewed-on: https://go-review.googlesource.com/75791
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

unix/syscall_openbsd.go

@@ -107,6 +107,45 @@ func setattrlistTimes(path string, times []Timespec, flags int) error {
 	return ENOSYS
 }
 
+//sys	ioctl(fd int, req uint, arg uintptr) (err error)
+
+// ioctl itself should not be exposed directly, but additional get/set
+// functions for specific types are permissible.
+
+// IoctlSetInt performs an ioctl operation which sets an integer value
+// on fd, using the specified request number.
+func IoctlSetInt(fd int, req uint, value int) error {
+	return ioctl(fd, req, uintptr(value))
+}
+
+func IoctlSetWinsize(fd int, req uint, value *Winsize) error {
+	return ioctl(fd, req, uintptr(unsafe.Pointer(value)))
+}
+
+func IoctlSetTermios(fd int, req uint, value *Termios) error {
+	return ioctl(fd, req, uintptr(unsafe.Pointer(value)))
+}
+
+// IoctlGetInt performs an ioctl operation which gets an integer value
+// from fd, using the specified request number.
+func IoctlGetInt(fd int, req uint) (int, error) {
+	var value int
+	err := ioctl(fd, req, uintptr(unsafe.Pointer(&value)))
+	return value, err
+}
+
+func IoctlGetWinsize(fd int, req uint) (*Winsize, error) {
+	var value Winsize
+	err := ioctl(fd, req, uintptr(unsafe.Pointer(&value)))
+	return &value, err
+}
+
+func IoctlGetTermios(fd int, req uint) (*Termios, error) {
+	var value Termios
+	err := ioctl(fd, req, uintptr(unsafe.Pointer(&value)))
+	return &value, err
+}
+
 /*
  * Exposed directly
  */
@@ -227,7 +266,6 @@ func setattrlistTimes(path string, times []Timespec, flags int) error {
 // getresuid
 // getrtable
 // getthrid
-// ioctl
 // ktrace
 // lfs_bmapv
 // lfs_markv