Release 2.6.4

• Same code as 2.6.3. The tag of release 2.6.3 was moved after package managers (Homebrew) had picked up the original source archive, so its checksum changed. Please use 2.6.4 instead of 2.6.3.
• Copies of 2.6.3 obtained before this release (e.g. the Homebrew bottle) may be based on an earlier state of the code, which lacks the last fixes, e.g. for exit, the handling of errors at the top level, and the command-line parsing of LispKitRepl.
• For the changes since 2.6.2 see the notes of release 2.6.3 and the changelog.