Merge branch 'lua-ffi-structs' into 'master'

lua ffi bindings: fix incorrect structs

Some structures have changed but lua was still using the old ABI.
I think no our lua code used the fields misplaced due to this,
except an example in documentation.

I didn't check much of the ABI in there.  I wish I knew some
(half-)automatic way how to do that.

See merge request !68