package/watchdog: new package

package/watchdog: new package

watchdog is a flexible watchdog daemon that improves on the already
available Busybox watchdog daemon by providing more advanced features,
like defining custom system status checks and executing repair scripts
to react upon invariants that don't hold.

Due to "watchdog" being also provided by Busybox, we need to make that
package/watchdog installs the watchdog binary in the same place as
Busybox (i.e in /sbin), and need to add a dependency of Busybox on
this new watchdog package.

Signed-off-by: Alejandro González <alejandro.gonzalez.correo@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>