capgen: update for StdLength -> DefaultLen rename.
capgen: update for StdLength -> DefaultLen rename.

msn217/captcha,gotomypc/captcha,thomasmodeneis/captcha,eleme/fork_captcha,ZiRo-/captcha,dchest/captcha,zj8487/captcha,ZiRo-/captcha,kaz8/go-captcha,rainyear/captcha,oblank/captcha