5.4.0

CHANGES:

Added

• connection#socket_descr, which exposes the libpq socket as a
  Unix.file_descr suitable for readiness-based waiting without Obj.magic.

Changed

• Updated asynchronous and notification examples to use socket_descr instead
  of coercing socket with Obj.magic.

Fixed

• string_of_error now normalizes trailing newlines in backend-provided error
  messages and avoids odd punctuation for empty Unexpected_status details.