responses.

Processing controller actions in a separate thread allows us to work
around the rack api - we can allow the user to set status and headers,
then block until the first bytes are written.  As soon as the first
bytes are written, the main thread can return the status, headers, and
(essentially) a queue for the body.

Fix incorrect usage `require mysql` in the activerecord/.../mysql_rake_test

Documentation Fix: Pointing the case when no dependent option is given to a association method

More polite cleanup for sqlite tests

DRY class_attribute

See the comment in the file activerecord/lib/active_record.rb
added by this patch for the rationale.

Fix test_can_wait_until_commit(ResponseTest) in /actionpack/test/dispatch/response_test.rb

Refactor to reset_table_name

This require makes the dependency even more clear.
In particular we are eager loading the session
store but that does not work if AR is used
outside Rails, this patch is preliminary work
in fixing #7160.

This file uses mattr_accessor.

This reverts commit 14fc8b34.

Reason: we need to discuss a better path from this removal.

Conflicts:
	activerecord/lib/active_record/reflection.rb
	activerecord/test/cases/base_test.rb
	activerecord/test/models/developer.rb

Modity the :json_data_empty attribute from `:null => false` to `:null => true`

Don't test language-level exception messages

Ruby implementations should be free to produce exception
messages that are not identical to MRI. For example,
Rubinius produces 'Expected an even number, got 5'.

to address ORA-01400 errors with Oracle enhanced adapter.

The original commit 3c0bf043 requires :json_data_empty attribute
has empty string OR null, then setting `:default => ""` is enough.

Validates_presence_of associated object marked for destruction

 will now return nil instead of raise a NoMethodError if the receiving object does not implement the method