This is more robust, faster, and incidentally gets rid of remaining
"error in the finalization thread: Bad file descriptor" messages.
* gnu/services/base.scm (unicode-start): Rewrite to use 'tcgetattr' and
'tcsetattr'.
(console-font-shepherd-services)[start]: Add 'loop' to check whether
DEVICE is ready. Tolerate EX_OSERR return from 'setfont'.
[modules]: New field.