openid_provider 6.x-1.0-rc2

With this release we complete the checkid_immediate implementation and perform further code cleanup. With this release, there remains no TODOs directly in the code (although some things are still missing, according to the README).

* fix warnings in PHP 5.3 (corollary of #1421536: Module is broken at install)
* generate a association handle if it's invalid, to follow the standard
* finish the checkid_immediate implementation by returning an error if we need to prompt the user
* handle properly the case where we do not supported the requested association type