New versions

[madsmtm]

Also fixes https://github.com/madsmtm/objc2/issues/268.

Checklist

• [x] The branch is named new-versions, such that the full CI will run.
• [x] Changelogs have only been modified under the Unreleased header.
• [x] Version numbers are bumped in the following order:
  • objc2-proc-macros (no significant changes)
  • objc-sys
  • objc2-encode
  • block-sys (no significant changes)
  • objc2
  • block2
  • icrate
• Local tests have been run (see helper-scripts/test-local.fish):
  • [x] macOS 10.14.6 32bit
  • [x] iOS 9.3.6, 1st generation iPad Mini

Post merge:

• [ ] A tag is created on the merge commit for each new version.

[madsmtm]

icrate v0.1.0 not released (yet) due to https://github.com/madsmtm/objc2/issues/537