See issue #3955
the intention is to deprecate [advancefrom] in
favour of [modify_unit_type], because it was a
common source of OOS errors, and it is less flexible.
As a secondary effect this also fixes issue #4402 :
"changing units via extra_defines sometimes not working
because extra_defines had bugs".
Now we no longer use extra_defines for that.
Addon authors should now no longer use these extra_defines,
instead put the new core marcos with the same name directly
into [campaign].