syscall: add Flock_t on Linux

Matches Darwin and the BSDs. This means leveldb-go, kv,
Camlistore, etc can stop defining these structs on Linux by
hand.

Update #7059

R=golang-codereviews, dave, iant
CC=golang-codereviews
https://golang.org/cl/53350043

src/pkg/syscall/consistency_unix_test.go

@@ -32,3 +32,13 @@ func _() {
 		_ int = syscall.TCOFLUSH
 	)
 }
+
+func _() {
+	_ = syscall.Flock_t{
+		Type:   int16(0),
+		Whence: int16(0),
+		Start:  0,
+		Len:    0,
+		Pid:    int32(0),
+	}
+}

src/pkg/syscall/types_linux.go

@@ -158,6 +158,8 @@ type Dirent C.struct_dirent
 
 type Fsid C.fsid_t
 
+type Flock_t C.struct_flock
+
 // Sockets
 
 type RawSockaddrInet4 C.struct_sockaddr_in

src/pkg/syscall/ztypes_linux_386.go

@@ -142,6 +142,14 @@ type Fsid struct {
 	X__val [2]int32
 }
 
+type Flock_t struct {
+	Type   int16
+	Whence int16
+	Start  int64
+	Len    int64
+	Pid    int32
+}
+
 type RawSockaddrInet4 struct {
 	Family uint16
 	Port   uint16

src/pkg/syscall/ztypes_linux_amd64.go

@@ -142,6 +142,16 @@ type Fsid struct {
 	X__val [2]int32
 }
 
+type Flock_t struct {
+	Type      int16
+	Whence    int16
+	Pad_cgo_0 [4]byte
+	Start     int64
+	Len       int64
+	Pid       int32
+	Pad_cgo_1 [4]byte
+}
+
 type RawSockaddrInet4 struct {
 	Family uint16
 	Port   uint16

src/pkg/syscall/ztypes_linux_arm.go

@@ -144,6 +144,14 @@ type Fsid struct {
 	X__val [2]int32
 }
 
+type Flock_t struct {
+	Type   int16
+	Whence int16
+	Start  int64
+	Len    int64
+	Pid    int32
+}
+
 type RawSockaddrInet4 struct {
 	Family uint16
 	Port   uint16