message: Let canonicalize_address report user errors
diff: sends invalid UTF-8 in places that expect strings.
  - Remove `FfiError::Other` in favour of `FfiError::UserErr` and
  `FfiError::Unknown`.
  +- The `canonicalize_address` import now reports user errors to the contract.
  ## 0.9.4 (2020-07-16)
  