Update drupal7 pacakge to 7.23.

Drupal 7.23, 2013-08-07
-----------------------
- Fixed a fatal error on PostgreSQL databases when updating the Taxonomy module
  from Drupal 6 to Drupal 7.
- Fixed the default ordering of CSS files for sites using right-to-left
  languages, to consistently place the right-to-left override file immediately
  after the CSS it is overriding (API change: https://drupal.org/node/2058463).
- Added a drupal_check_memory_limit() API function to allow the memory limit to
  be checked consistently (API addition).
- Changed the default web.config file for IIS servers to allow favicon.ico
  files which are present in the filesystem to be accessed.
- Fixed inconsistent support for the 'tel' protocol in Drupal's URL filtering
  functions.
- Performance improvement: Allowed all hooks to be included in the
  module_implements() cache, even those that are only invoked on HTTP POST
  requests.
- Made the database system replace truncate queries with delete queries when
  inside a transaction, to fix issues with PostgreSQL and other databases.
- Fixed a bug which caused nested contextual links to display improperly.
- Fixed a bug which prevented cached image derivatives from being flushed for
  private files and other non-default file schemes.
- Fixed drupal_render() to always return an empty string when there is no
  output, rather than sometimes returning NULL (minor API change).
- Added protection to cache_clear_all() to ensure that non-cache tables cannot
  be truncated (API addition: a new isValidBin() method has been added to the
  default database cache implementation).
- Changed the default .htaccess file to support HTTP authorization in CGI
  environments.
- Changed the password reset form to pre-fill the username when requested via a
  URL query parameter, and used this in the error message that appears after a
  failed login attempt (minor data structure and behavior change).
- Fixed broken support for foreign keys in the field API.
- Fixed "No active batch" error when a user cancels their own account.
- Added a description to the "access content overview" permission on the
  permissions page (string change).
- Added a drupal_array_diff_assoc_recursive() function to allow associative
  arrays to be compared recursively (API addition).
- Added human-readable labels to image styles, in addition to the existing
  machine-readable name (API change: https://drupal.org/node/2058503).
- Moved the drupal_get_hash_salt() function to bootstrap.inc and used it in
  additional places in the code, for added security in the case where there is
  no hash salt in settings.php.
- Fixed a regression in Drupal 7.22 that caused internal server errors for
  sites running on very old Apache 1.x web servers.
- Numerous small bug fixes.
- Numerous API documentation improvements.
- Additional automated test coverage.


(taca)