simpletest 6.x-2.3

From CHANGELOG.txt:

SimpleTest 6.x-2.3, 2008-09-15
------------------------------
- Backports:
    * #297869: Add xpath method to SimpleTest.
    * #297894: Add assertLink and assertNoLink to SimpleTest.
    * #298137: drupalCreateContentType() should reset node permissions.
    * #268148: Don't verify SSL certificates.
    * #293099: Clarify form documentation and error handling.
    * #296027: {simpletest} indexes come with wrong array expression.
    * #299461: assertEqual() does not work with arrays.
    * #246261: Simpletest-light doesn't handle selects with <optgroup>'s correctly.
- Changes:
    * #297890: Add notice to INSTALL.txt instructing users on Windows to
               encode settings file with the UNIX standard.
    * #302606: Usability: improve installation error message.