Make ActiveSupport::Inflector locale aware and multilingual

AR::Relation#order: make new order prepend old one.

    User.order("name asc").order("created_at desc")
    # SELECT * FROM users ORDER BY created_at desc, name asc

This also affects order defined in `default_scope` or any kind of associations.

The Inflector is currently not very supportive of internationalized
websites. If a user wants to singularize and/or pluralize words based on
any locale other than English, they must define each case in locale
files. Rather than create large locale files with mappings between
singular and plural words, why not allow the Inflector to accept a
locale?

This patch makes ActiveSupport::Inflector locale aware and uses `:en`` unless
otherwise specified. Users will still be provided a list of English (:en)
inflections, but they may additionally define inflection rules for other
locales. Each list is kept separately and permanently. There is no reason to
limit users to one list of inflections:

    ActiveSupport::Inflector.inflections(:es) do |inflect|
      inflect.plural(/$/, 's')
      inflect.plural(/([^aeéiou])$/i, '\1es')
      inflect.plural(/([aeiou]s)$/i, '\1')
      inflect.plural(/z$/i, 'ces')
      inflect.plural(/á([sn])$/i, 'a\1es')
      inflect.plural(/é([sn])$/i, 'e\1es')
      inflect.plural(/í([sn])$/i, 'i\1es')
      inflect.plural(/ó([sn])$/i, 'o\1es')
      inflect.plural(/ú([sn])$/i, 'u\1es')

      inflect.singular(/s$/, '')
      inflect.singular(/es$/, '')

      inflect.irregular('el', 'los')
    end

    'ley'.pluralize(:es)   # => "leyes"
    'ley'.pluralize(:en)   # => "leys"
    'avión'.pluralize(:es) # => "aviones"
    'avión'.pluralize(:en) # => "avións"

A multilingual Inflector should be of use to anybody that is tasked with
internationalizing their Rails application.
Signed-off-by: NDavid Celis <david@davidcelis.com>

Fix nodoc in metal/live [ci skip]

fix typo in metal/live [ci skip]

update_column was suggested as replacement of update_attribute at the
last release of 3-2-stable, so deprecating it now will confuse the
users.

class_attribute is a building block and using define_method
can be much slower for such basic method definitions.

This reverts commit d59208d7.

Refactor ActionDispatch::Http::Cache::Response#cache_control_headers

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