version: Use +git suffix

Signed-off-by: Frank Terbeck <ft@bewatermyfriend.org>
(termios system): Define more constants

Signed-off-by: Frank Terbeck <ft@bewatermyfriend.org>
gen-gps: Use #f if a constant is undefined

Signed-off-by: Frank Terbeck <ft@bewatermyfriend.org>
gen-gps: Use hexadecimal integer literals

Signed-off-by: Frank Terbeck <ft@bewatermyfriend.org>