This is done for forwards compatibility, in case something that is
currently an alias becomes a unique locale in the future.

This means that the value of C<id()> and the object's class may not
match.

The loaded locale is cached, so that B<locale objects may be
singletons>.  Calling C<register()>, C<add_aliases()>,
or C<remove_alias()> clears the cache.

=item * ids

  my @ids = DateTime::Locale->ids;
  my $ids = DateTime::Locale->ids;

Returns an unsorted list of the available locale ids, or an array
reference if called in a scalar context.  This list does not include
aliases.

=item * names

  my @names = DateTime::Locale->names;
  my $names = DateTime::Locale->names;

Returns an unsorted list of the available locale names in English, or
an array reference if called in a scalar context.

=item * native_names

  my @names = DateTime::Locale->native_names;
  my $names = DateTime::Locale->native_names;

Returns an unsorted list of the available locale names in their native
language, or an array reference if called in a scalar context. All
native names are utf8 encoded.

B<NB>: Many locales are only partially translated, so some native
locale names may still contain some English.

=item * add_aliases ( $alias1 => $id1, $alias2 => $id2, ... )

Adds an alias to an existing locale id. This allows a locale to be
C<load()>ed by its alias rather than id or name. Multiple aliases are
allowed.

If the passed locale id is neither registered nor listed in
L</AVAILABLE LOCALES>, an exception is thrown.

 DateTime::Locale->add_aliases( LastResort => 'es_ES' );

 # Equivalent to DateTime::Locale->load('es_ES');
 DateTime::Locale->load('LastResort');

You can also pass a hash reference to this method.

 DateTime::Locale->add_aliases( { Default     => 'en_GB',
                                  Alternative => 'en_US',
                                  LastResort  => 'es_ES' } );

=item * remove_alias( $alias )

Removes a locale id alias, and returns true if the specified alias
actually existed.

 DateTime::Locale->add_aliases( LastResort => 'es_ES' );

 # Equivalent to DateTime::Locale->load('es_ES');
 DateTime::Locale->load('LastResort');

 DateTime::Locale->remove_alias('LastResort');

 # Throws an exception, 'LastResort' no longer exists
 DateTime::Locale->load('LastResort');

=item * register( { ... }, { ... } )

This method allows you to register custom locales with the module.  A
single locale is specified as a hash, and you may register multiple
locales at once by passing an array of hash references.

Until registered, custom locales cannot be instantiated via C<load()>
and will not be returned by querying methods such as C<ids()> or
C<names()>.

 register( id               => $locale_id,
           en_language      => ..., # something like 'English' or 'Afar',

           # All other keys are optional.  These are:
           en_script    => ...,
           en_territory => ...,
           en_variant   => ...,

           native_language  => ...,
           native_sript     => ...,
           native_territory => ...,
           native_variant   => ...,

           # Optional - defaults to DateTime::Locale::$locale_id
           class                => $class_name,