…2086)

While continuing the work on #2011, I realized that constant
declarations have a problem when using `iota`. I mean, it technically
works, but const *blocks* we not supported which means that setting all
constants to `iota` as shown in the documentation was non-sensical, as
`iota` resets every time outside of const blocks.

So, this is between the bug fix and the feature. To me, it's a bug fix
as the behavior wasn't the one intended when creating extgen.