this was necessary for the tests, yet they still don't work

not sure whether this is the way to go, but at least it works

especially if we want to assign terminals dynamically, we cannot assing
terminals to loops at creation time.

we just try a random address, that works most of the time

there should be a test for this.

this breaks a bit the logic of terminals, but is necessary for
bootstrapping: you want to know which type of terminal it is before
we initialize it.

constantly assure that the terminals are in operational mode.

They should not drop out of operational, but if we are slow, they
do.

this is tested with read hardware, the tests obviously don't work,
we have to grandfather them.

very old terminals do not have SDO definitions, but have their
PDO mapping defined in the eeprom. Namely the EK1814. This makes
this particular terminal work, let's hope it also works for similar
terminals.

if a device is only reading from terminals, it can be added to
several sync groups. Start to build this concept and improve
tests.

the use of hashmaps is just hopelessly outdated.

See merge request teichman/ebpfcat!16

with the PacketVar descriptor, one can simply address data in packets.

this also adds support for network byte order, and minor improvements.

See merge request teichman/ebpfcat!15

this also improves readabiliy

especially the reverse divisions were incorrect. Now the code
is shorter as well.

this modifies the tests to do some multiplication not long -
but it actually seems legit.

this makes a difference with signed extension to 64 bit

this is not actually related to the ebpfcat PacketVar, but kinda
similar.