syscall: prepare for 64-bit ints

This CL fixes code that incorrectly assumes that int is 32 bits wide.
Specifically, the socketpair system call expects a pointer to a pair
of int32s, not a pair of ints. Fix this inside the wrappers without
changing the APIs.

Update #2188.

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/6552063

src/pkg/syscall/zsyscall_netbsd_386.go

diff --git a/src/pkg/syscall/zsyscall_netbsd_386.go b/src/pkg/syscall/zsyscall_netbsd_386.go
index ee3b540..3b84c4f 100644
--- a/src/pkg/syscall/zsyscall_netbsd_386.go
+++ b/src/pkg/syscall/zsyscall_netbsd_386.go
@@ -131,7 +131,7 @@
 
 // THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
 
-func socketpair(domain int, typ int, proto int, fd *[2]int) (err error) {
+func socketpair(domain int, typ int, proto int, fd *[2]int32) (err error) {
 	_, _, e1 := RawSyscall6(SYS_SOCKETPAIR, uintptr(domain), uintptr(typ), uintptr(proto), uintptr(unsafe.Pointer(fd)), 0, 0)
 	if e1 != 0 {
 		err = e1