unix: add IoctlGetInt and IoctlSetInt on Linux

This CL adds basic integer get/set functions which wrap a generic
ioctl call.  The API is similar the one introduced for solaris/amd64
in CL 14587, but the request parameter has been changed to a uint
instead of an int.  This makes requests with a number larger than the
maximum signed 32-bit integer work on linux/386.

For consistency, the solaris/amd64 API has also been updated to make
use of a uint instead of an int for the request number.

Fixes golang/go#20474

Change-Id: Iaae1ee2e4bb4bfcc420dcec252fe53c8d90ce81d
Reviewed-on: https://go-review.googlesource.com/44009
Run-TryBot: Matt Layher <mdlayher@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
diff --git a/unix/zsyscall_linux_mips64.go b/unix/zsyscall_linux_mips64.go
index dfa9d93..5a496a9 100644
--- a/unix/zsyscall_linux_mips64.go
+++ b/unix/zsyscall_linux_mips64.go
@@ -14,6 +14,16 @@
 
 // THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
 
+func ioctl(fd int, req uint, arg uintptr) (err error) {
+	_, _, e1 := Syscall(SYS_IOCTL, uintptr(fd), uintptr(req), uintptr(arg))
+	if e1 != 0 {
+		err = errnoErr(e1)
+	}
+	return
+}
+
+// THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
+
 func Linkat(olddirfd int, oldpath string, newdirfd int, newpath string, flags int) (err error) {
 	var _p0 *byte
 	_p0, err = BytePtrFromString(oldpath)