* Unbreak OTA on crappy shells
Very, very old ash versions abort on set -o failures (as mandated by
POSIX, granted). This makes it impossible to reliably catch failures in
a single step.
So do it from the Lua side instead.
Should fix#5844
* Launch the zsync wrapper through bash on Cervantes
Update shellcheck and shfmt to the latest version.
Fixes <https://github.com/koreader/koreader/issues/5152>.
Btw, you can apply shellcheck suggestions with a command like:
```
shellcheck --include=SC2250 -f diff *.sh | git apply
```
* remove unused setting 'internal_storage_mount_point
use filemanagerutil.getDefaultDir() instead
https://github.com/koreader/koreader/blob/master/frontend/apps/filemanager/filemanagerutil.lua#L15
* more info about device frontlight/naturalLight capabilities
* make stock reader fonts available in KOReader
* remove restore-wifi-async leftovers
* wireless: fix wpa_supplicant configuration:
make it compatible w/ debian wheezy binaries
don't try to run enable-wifi.sh more than once
