ipv6: rename freebsd32o64 with compatFreeBSD32 for consistency

The variable name compatFreeBSD32 refers to the kernel configuration
directive COMPAT_FREEBSD32 and is also used in route and ipv6 packages.

Change-Id: I00e6de390c25b7df45b76e772719a83fa6b0843b
Reviewed-on: https://go-review.googlesource.com/c/149879
Reviewed-by: Ian Lance Taylor <iant@golang.org>

Author: mikioh

Diff for: ipv6/sys_freebsd.go

@@ -51,7 +51,7 @@ func init() {
 		archs, _ := syscall.Sysctl("kern.supported_archs")
 		for _, s := range strings.Fields(archs) {
 			if s == "amd64" {
-				freebsd32o64 = true
+				compatFreeBSD32 = true
 				break
 			}
 		}

Diff for: ipv6/sys_ssmreq.go

@@ -13,7 +13,7 @@ import (
 	"golang.org/x/net/internal/socket"
 )
 
-var freebsd32o64 bool
+var compatFreeBSD32 bool // 386 emulation on amd64
 
 func (so *sockOpt) setGroupReq(c *socket.Conn, ifi *net.Interface, grp net.IP) error {
 	var gr groupReq
@@ -22,7 +22,7 @@ func (so *sockOpt) setGroupReq(c *socket.Conn, ifi *net.Interface, grp net.IP) e
 	}
 	gr.setGroup(grp)
 	var b []byte
-	if freebsd32o64 {
+	if compatFreeBSD32 {
 		var d [sizeofGroupReq + 4]byte
 		s := (*[sizeofGroupReq]byte)(unsafe.Pointer(&gr))
 		copy(d[:4], s[:4])
@@ -41,7 +41,7 @@ func (so *sockOpt) setGroupSourceReq(c *socket.Conn, ifi *net.Interface, grp, sr
 	}
 	gsr.setSourceGroup(grp, src)
 	var b []byte
-	if freebsd32o64 {
+	if compatFreeBSD32 {
 		var d [sizeofGroupSourceReq + 4]byte
 		s := (*[sizeofGroupSourceReq]byte)(unsafe.Pointer(&gsr))
 		copy(d[:4], s[:4])