Examples which used the ancient spec-version v1.2 have been updated to
use at least v1.8; and use CPP-Options instead of GHC-Options where
`cabal check` would have warned; avoid automatic flags for features;
also be explicit about the `build-type:` to avoid the implicit `Custom`
default (TODO: we should really change the default with a future
spec-version to `Simple`)

[skip ci]