Don't clear c_cflag when setting raw mode on our tty.
Don't clear c_cflag when setting raw mode on our tty.

This makes tcsetattr return EINVAL on some systems, and there
shouldn't be any flags in there we care about.

nelhage/reptyr,yatsek/reptyr,nelhage/reptyr,jerome-pouiller/reredirect,developerfm/reptyr,developerfm/reptyr,yatsek/reptyr,jerome-pouiller/reredirect,yatsek/reptyr,developerfm/reptyr,nelhage/reptyr