MDL-24694 fixing broken upgrade once more - this step was skipped because two blocks had the same version number

- added message provider to manage assignment's messaging
- user_preferences.name length changed form 50 to 255 due to long messaging preference names.

MDL-24772 fixed a theoritical problem with sites that do not have any enrollable roles with moodle/course:view, credit goes to Tim Lock

registration MDL-24641 get language code from the full language list codes, not from the Moodle language package code

MDL-24302 removing multiple field from block table in install.xml - it was already removed in upgrade once

* handlers can be defined as internal or external
* external handlers are not called instantly when inside DB transaction
* code cleanup
* more robust detection of broken handlers
* refixed unit tests
* removing all pending events from 1.9 - these can not be processed due to encoding changes
* finally using real 'component' in handlers table

blocks upgrade MDL-22693 We also need to drop another old index, on sites that were upgraded from 1.9

community hub MDL-24215 change the site secret key for get_site_identifier in the registration process => increase the DB field size + change the confirmation form to the get_site_identifier TEXT format

MDL-24116 dropping tables that were used in old xmldb test suite, the tests will be moved to functional db tests in subsequent commits

blocks upgrade MDL-22693 Forgot to change the precision of the block_instances.pagetypepattern column to 64 chars. Do it now.
You have to drop and re-create the associated index, otherwise this will not work, at least on Postgres.

MDL-23885 flattening filepool directory structure - hopefully this will lower the number of directories but still keep a reasonable number of files in each directory on large installs; see tracker for more details

MDL-22001 filter_text() and filter_string() now use context parameter instead of courseid, PAGE->context is used only as a fallback; moved comment stuff away from format_text() because it does not belong there; filterlib is not using courseid except for legacy filters; fixed coding style in filters;Êimproved php docs; fixed upgrade of filters (should be in plugins, not core)

webservice MDL-23341 add required capabilities to the service function declaration (lib/services.php), display missing capaibilities for users linked to a token and for authorised users, display function capabilities, refactor service add function page

MDL-21840 backup - table for files handling on restore. Big thanks to MySQL for being so... limited?

The tables were used for caching of XML-RPC results only, no upgrade is
needed. The functionality of these tables is now handled by new tables
defined by mnetservice_enrol plugin.