Add support for MikroTik RB5009UG

I decided to check the version about packing the RouterBoot with the UCL NRV2B algorithm - without much hope for success!
But oddly enough, the first unpacking utility that I found: nrv2b was able to unpack it!
I took the RouterBoot file from RouterOS at /etc/70x0-7.2rc1.fwf and then do:

dd if=./70x0-7.2rc1.fwf of=./routerboot-7.2rc1.enc bs=4 skip=9
./nrv2b/nrv2b d routerboot-7.2rc1.enc ./routerboot-7.2rc1.dec

It remains to understand how this can be translated into assembly code ...