Log Message:
Update ruby-sequel to 3.39.0.

=== 3.39.0 (2012-09-01)

* Fix defaults_setter to set false default values (jeremyevans)

* Fix serial sequence query in Database#primary_key_sequence on PostgreSQL
  (jeremyevans) (#538)

* Add Database#copy_into when using postgres adapter with pg driver, for very
  fast inserts into tables (jeremyevans)

* Combine multiple alter_table operations into a single query where possible
  on MySQL and PostgreSQL (jeremyevans)

* Handle sets of alter_table operations on MySQL and MSSQL where later
  operations depend on earlier ones (jeremyevans)

* Add constraint_validations plugin for automatic validations of constaints
  defined by extension (jeremyevans)

* Add constraint_validations extension for defining database constraints
  similar to validations (jeremyevans)

* Add Database#supports_regexp? for checking for regular expression support
  (jeremyevans)

* Add Sequel.trim for cross platform trim function (jeremyevans)

* Add Sequel.char_length for cross platform char_length function (jeremyevans)

* Fixing caching of MySQL server version (hannesg) (#536)

* Allow overriding the convert_tinyint_to_bool setting on a per-Dataset basis
  in the mysql and mysql2 adapters (jeremyevans)

* Make ValidationFailed and HookFailed exceptions have model method that
  returns the related model (jeremyevans)

* Automatically wrap array arguments to most PGArrayOp methods in PGArrays
  (jeremyevans)

* Add set_column_not_null to alter table generator for marking a column as not
  null (jeremyevans)

* Default second argument of set_column_allow_null to true in alter table
  generator (jeremyevans)

* Allow Dataset#count to take an argument or virtual row block (jeremyevans)

* Attempt to recognize CURRENT_{DATE,TIMESTAMP} defaults and return them as
  Sequel::CURRENT_{DATE,TIMESTAMP} (jeremyevans)

* Make dataset.insert(model) assume a single column if model uses the pg_row
  plugin (jeremyevans)

* No longer handle model instances in plain (non-model) datasets when
  inserting (jeremyevans)

* Use subselects for model classes as tables in join methods in model datasets
  if the model's dataset isn't a simple select (jeremyevans)

* No longer handle model classes as tables in join/graph methods in plain
  (non-model) datasets (jeremyevans)

* Make Time->DateTime and DateTime->Time typecasts retain fractional seconds
  on ruby 1.8 (jeremyevans) (#531)

* Add bin/sequel -c support, for running code string instead of using an IRB
  prompt (jeremyevans)

* Allow subclasses plugin to take a block, which is called with each
  subclasses created (jeremyevans)

* Add :where option to validates_unique, for custom uniqueness filters
  (jeremyevans)

* Add :connection_handling=>:disconnect option for threaded connection pools
  (jeremyevans)

* Add Postgres::PGRowOp#* for referencing the members of the composite type as
  separate columns (jeremyevans)

* Make identity_map plugin work with models lacking a primary key (jeremyevans)

* Recognize MySQL set type and default value (jeremyevans) (#529)