syscall: add syscall.Termios on freebsd/{386,amd64}

R=golang-codereviews, bradfitz, mg
CC=golang-codereviews
https://golang.org/cl/51580044

src/pkg/syscall/types_freebsd.go

@@ -18,6 +18,7 @@ package syscall
 #include <dirent.h>
 #include <fcntl.h>
 #include <signal.h>
+#include <termios.h>
 #include <stdio.h>
 #include <unistd.h>
 #include <sys/event.h>
@@ -248,3 +249,7 @@ type BpfInsn C.struct_bpf_insn
 type BpfHdr C.struct_bpf_hdr
 
 type BpfZbufHeader C.struct_bpf_zbuf_header
+
+// Terminal handling
+
+type Termios C.struct_termios

src/pkg/syscall/ztypes_freebsd_386.go

@@ -443,3 +443,13 @@ type BpfZbufHeader struct {
 	User_gen   uint32
 	X_bzh_pad  [5]uint32
 }
+
+type Termios struct {
+	Iflag  uint32
+	Oflag  uint32
+	Cflag  uint32
+	Lflag  uint32
+	Cc     [20]uint8
+	Ispeed uint32
+	Ospeed uint32
+}

src/pkg/syscall/ztypes_freebsd_amd64.go

@@ -446,3 +446,13 @@ type BpfZbufHeader struct {
 	User_gen   uint32
 	X_bzh_pad  [5]uint32
 }
+
+type Termios struct {
+	Iflag  uint32
+	Oflag  uint32
+	Cflag  uint32
+	Lflag  uint32
+	Cc     [20]uint8
+	Ispeed uint32
+	Ospeed uint32
+}