Unix: move from syscall to golang.org/x/sys/unix

Prepare to using `unix.TCFLSH`/`unix.TIOCFLUSH`
which is missing in `syscall` package

serial_darwin_386.go

@@ -6,38 +6,38 @@
 
 package serial // import "go.bug.st/serial.v1"
 
-import "syscall"
+import "golang.org/x/sys/unix"
 
 // termios manipulation functions
 
 var baudrateMap = map[int]uint32{
-	0:      syscall.B9600, // Default to 9600
-	50:     syscall.B50,
-	75:     syscall.B75,
-	110:    syscall.B110,
-	134:    syscall.B134,
-	150:    syscall.B150,
-	200:    syscall.B200,
-	300:    syscall.B300,
-	600:    syscall.B600,
-	1200:   syscall.B1200,
-	1800:   syscall.B1800,
-	2400:   syscall.B2400,
-	4800:   syscall.B4800,
-	9600:   syscall.B9600,
-	19200:  syscall.B19200,
-	38400:  syscall.B38400,
-	57600:  syscall.B57600,
-	115200: syscall.B115200,
-	230400: syscall.B230400,
+	0:      unix.B9600, // Default to 9600
+	50:     unix.B50,
+	75:     unix.B75,
+	110:    unix.B110,
+	134:    unix.B134,
+	150:    unix.B150,
+	200:    unix.B200,
+	300:    unix.B300,
+	600:    unix.B600,
+	1200:   unix.B1200,
+	1800:   unix.B1800,
+	2400:   unix.B2400,
+	4800:   unix.B4800,
+	9600:   unix.B9600,
+	19200:  unix.B19200,
+	38400:  unix.B38400,
+	57600:  unix.B57600,
+	115200: unix.B115200,
+	230400: unix.B230400,
 }
 
 var databitsMap = map[int]uint32{
-	0: syscall.CS8, // Default to 8 bits
-	5: syscall.CS5,
-	6: syscall.CS6,
-	7: syscall.CS7,
-	8: syscall.CS8,
+	0: unix.CS8, // Default to 8 bits
+	5: unix.CS5,
+	6: unix.CS6,
+	7: unix.CS7,
+	8: unix.CS8,
 }
 
 const tcCMSPAR uint32 = 0 // may be CMSPAR or PAREXT