kexecboot: upgrade and move to git tag 0daa77

* new git repository on github
* new LABEL separator
* text-ui fallback
* install /sys for upcoming ubifs detection
* menu-bug fix
* minor fixes

Signed-off-by: Andrea Adami <andrea.adami@gmail.com>
Signed-off-by: Koen Kooi <koen@dominion.thruhere.net>