vendor: update all dependencies

* Update all dependencies
  * Remove all `[[constraint]]` from Gopkg.toml
  * Add in the minimum number of `[[override]]` to build
  * Remove go get of github.com/inconshreveable/mousetrap as it is vendored
  * Update docs with new policy on constraints

vendor/golang.org/x/sys/unix/syscall_unix.go

@@ -9,6 +9,7 @@ package unix
 import (
 	"bytes"
 	"runtime"
+	"sort"
 	"sync"
 	"syscall"
 	"unsafe"
@@ -51,6 +52,28 @@ func errnoErr(e syscall.Errno) error {
 	return e
 }
 
+// ErrnoName returns the error name for error number e.
+func ErrnoName(e syscall.Errno) string {
+	i := sort.Search(len(errorList), func(i int) bool {
+		return errorList[i].num >= e
+	})
+	if i < len(errorList) && errorList[i].num == e {
+		return errorList[i].name
+	}
+	return ""
+}
+
+// SignalName returns the signal name for signal number s.
+func SignalName(s syscall.Signal) string {
+	i := sort.Search(len(signalList), func(i int) bool {
+		return signalList[i].num >= s
+	})
+	if i < len(signalList) && signalList[i].num == s {
+		return signalList[i].name
+	}
+	return ""
+}
+
 // clen returns the index of the first NULL byte in n or len(n) if n contains no NULL byte.
 func clen(n []byte) int {
 	i := bytes.IndexByte(n, 0)
@@ -199,6 +222,13 @@ func Getpeername(fd int) (sa Sockaddr, err error) {
 	return anyToSockaddr(&rsa)
 }
 
+func GetsockoptByte(fd, level, opt int) (value byte, err error) {
+	var n byte
+	vallen := _Socklen(1)
+	err = getsockopt(fd, level, opt, unsafe.Pointer(&n), &vallen)
+	return n, err
+}
+
 func GetsockoptInt(fd, level, opt int) (value int, err error) {
 	var n int32
 	vallen := _Socklen(4)
@@ -206,6 +236,54 @@ func GetsockoptInt(fd, level, opt int) (value int, err error) {
 	return int(n), err
 }
 
+func GetsockoptInet4Addr(fd, level, opt int) (value [4]byte, err error) {
+	vallen := _Socklen(4)
+	err = getsockopt(fd, level, opt, unsafe.Pointer(&value[0]), &vallen)
+	return value, err
+}
+
+func GetsockoptIPMreq(fd, level, opt int) (*IPMreq, error) {
+	var value IPMreq
+	vallen := _Socklen(SizeofIPMreq)
+	err := getsockopt(fd, level, opt, unsafe.Pointer(&value), &vallen)
+	return &value, err
+}
+
+func GetsockoptIPv6Mreq(fd, level, opt int) (*IPv6Mreq, error) {
+	var value IPv6Mreq
+	vallen := _Socklen(SizeofIPv6Mreq)
+	err := getsockopt(fd, level, opt, unsafe.Pointer(&value), &vallen)
+	return &value, err
+}
+
+func GetsockoptIPv6MTUInfo(fd, level, opt int) (*IPv6MTUInfo, error) {
+	var value IPv6MTUInfo
+	vallen := _Socklen(SizeofIPv6MTUInfo)
+	err := getsockopt(fd, level, opt, unsafe.Pointer(&value), &vallen)
+	return &value, err
+}
+
+func GetsockoptICMPv6Filter(fd, level, opt int) (*ICMPv6Filter, error) {
+	var value ICMPv6Filter
+	vallen := _Socklen(SizeofICMPv6Filter)
+	err := getsockopt(fd, level, opt, unsafe.Pointer(&value), &vallen)
+	return &value, err
+}
+
+func GetsockoptLinger(fd, level, opt int) (*Linger, error) {
+	var linger Linger
+	vallen := _Socklen(SizeofLinger)
+	err := getsockopt(fd, level, opt, unsafe.Pointer(&linger), &vallen)
+	return &linger, err
+}
+
+func GetsockoptTimeval(fd, level, opt int) (*Timeval, error) {
+	var tv Timeval
+	vallen := _Socklen(unsafe.Sizeof(tv))
+	err := getsockopt(fd, level, opt, unsafe.Pointer(&tv), &vallen)
+	return &tv, err
+}
+
 func Recvfrom(fd int, p []byte, flags int) (n int, from Sockaddr, err error) {
 	var rsa RawSockaddrAny
 	var len _Socklen = SizeofSockaddrAny