Moving my functional test functions from posting_helpers.php to
posting_test.php since it is a bit nicer and more reusable if
posting_test.php is to be expanded in the future.
PHPBB3-8610
This will be used to test splitting/copying/merging/etc in functional tests
Also convert functional posting_test.php to use these functions
PHPBB3-8610
Users should not be deleted in tests that test user creation.
Tests should use unique user names to avoid collisions.
User deletion should use user_remove anyway.
PHPBB3-10972
Always add users, do not keep track of which users have been added.
The tests should know whether users they want exist or not.
Use more unique user names in tests for robustness.
Added some more assertions here and there.
PHPBB3-10972
