syscall: generate AT_* constants and regenerate ztypes_linux_*.go

Updates #9974

The *at family of syscalls requires some constants to be defined in the
syscall package for linux. Add the necessary constants and regenerate
the ztypes_linux_*.go files.

Change-Id: I6df343fef7bcacad30d36c7900dbfb621465a4fe
Reviewed-on: https://go-review.googlesource.com/5836Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/syscall/types_linux.go

@@ -377,6 +377,8 @@ type EpollEvent C.struct_my_epoll_event
 
 const (
 	_AT_FDCWD            = C.AT_FDCWD
+	_AT_REMOVEDIR        = C.AT_REMOVEDIR
+	_AT_SYMLINK_NOFOLLOW = C.AT_SYMLINK_NOFOLLOW
 )
 
 // Terminal handling

src/syscall/ztypes_linux_386.go

@@ -573,6 +573,8 @@ type EpollEvent struct {
 
 const (
 	_AT_FDCWD            = -0x64
+	_AT_REMOVEDIR        = 0x200
+	_AT_SYMLINK_NOFOLLOW = 0x100
 )
 
 type Termios struct {

src/syscall/ztypes_linux_amd64.go

@@ -591,6 +591,8 @@ type EpollEvent struct {
 
 const (
 	_AT_FDCWD            = -0x64
+	_AT_REMOVEDIR        = 0x200
+	_AT_SYMLINK_NOFOLLOW = 0x100
 )
 
 type Termios struct {

src/syscall/ztypes_linux_arm.go

@@ -562,6 +562,8 @@ type EpollEvent struct {
 
 const (
 	_AT_FDCWD            = -0x64
+	_AT_REMOVEDIR        = 0x200
+	_AT_SYMLINK_NOFOLLOW = 0x100
 )
 
 type Termios struct {

src/syscall/ztypes_linux_ppc64.go

@@ -579,6 +579,8 @@ type EpollEvent struct {
 
 const (
 	_AT_FDCWD            = -0x64
+	_AT_REMOVEDIR        = 0x200
+	_AT_SYMLINK_NOFOLLOW = 0x100
 )
 
 type Termios struct {

src/syscall/ztypes_linux_ppc64le.go

@@ -579,6 +579,8 @@ type EpollEvent struct {
 
 const (
 	_AT_FDCWD            = -0x64
+	_AT_REMOVEDIR        = 0x200
+	_AT_SYMLINK_NOFOLLOW = 0x100
 )
 
 type Termios struct {