= New Features

* A constant_sql_override Database extension has been added, allowing
  for overriding the SQL used by constants such as
  Sequel::CURRENT_TIMESTAMP.  This can be used to force
  CURRENT_TIMESTAMP to be literalized at a particular time zone:

    DB.extension :constant_sql_override
    DB.set_constant_sql(Sequel::CURRENT_TIMESTAMP,
      "CURRENT_TIMESTAMP AT TIME ZONE 'UTC'")

* Prepared statements now support the :single_value type, which
  returns the first column value in the dataset.

    prep_stmt = DB[:table].select(:column).prepare(:single_value, :ps)
    prep_stmt.call
    # PREPARE ps AS SELECT column FROM table LIMIT 1;
    # EXECUTE ps;
    # => 42

= Other Improvements

* Dataset#from_self will no longer use a cached dataset if any options
  are given, as that can result in incorrect behavior.

* Model.all in the static_cache plugin now accepts a block, mirroring
  the API when the static_cache plugin is not used.