Includes:
* update checker refactored to \core\update\ namespace
* plugininfo classes refactored to \core\plugininfo\ namespace
* plugin_manager renamed to core_plugin_manager
* redirect back to original page after plugin uninstall
* fixed assign subplugin uninstall
* move assign subplugins under the assignment in admin tree
* fixed plugininfo for all question related plugin types
* auth uninstall support
* added missing block dependencies
* added theme uninstall
* subplugin types are following the plugin on plugin overview page
* several performance improvements in plugin manager
* new warnigns when plugininfo are outdated or missing
* multiple fixes and other improvements

List of changes:
 * New OOP API using PHP namespace \core\session\.
 * All handlers now update the sessions table consistently.
 * Experimental DB session support in Oracle.
 * Full support for session file handler (filesystem locking required).
 * New option for alternative session directory.
 * Official memcached session handler support.
 * Workaround for memcached version with non-functional gc.
 * Improved security - forced session id regeneration.
 * Improved compatibility with recent PHP releases.
 * Fixed borked CSS during install in debug mode.
 * Switched to file based sessions in new installs.
 * DB session setting disappears if DB does not support sessions.
 * DB session setting disappears if session handler specified in config.php.
 * Fast purging of sessions used in request only.
 * No legacy distinction -  file, database and memcached support the same functionality.
 * Session handler name included in performance info.
 * Fixed user_loggedin and user_loggedout event triggering.
 * Other minor bugfixing and improvements.
 * Fixed database session segfault if MUC disposed before $DB.

Limitations:
 * Session access time is now updated right after session start.
 * Support for $CFG->sessionlockloggedinonly was removed.
 * First request does not update userid in sessions table.
 * The timeouts may break badly if server hosting forces PHP.ini session settings.
 * The session GC is a lot slower, we do not rely on external session timeouts.
 * There cannot be any hooks triggered at the session write time.
 * File and memcached handlers do not support session lock acquire timeouts.
 * Some low level PHP session functions can not be used directly in Moodle code.

This should resolve all html entity conversion problems in different PHP versions.

Comparison of arrays is not locale aware.

Thanks Eloy Lafuente for spotting my sloppy coding style!

1/ the sort flag can not use Intl extension constants because they may not be available
2/ add sort flag to all methods
3/ use private constructor instead of abstract - more Java like API to match the textlib
4/ add natural sorting support
5/ consistent bool return type
6/ better non-intl fallback
7/ more tests

Includes new textlib reset, new test for faulty integer lower/upper casing.

MDL-31142 fix textlib::substr() performance, invalid length in iconv_substr; use mbstring by default

MDL-31142 fix textlib::substr() performance, invalid length in iconv_substr; use mbstring by default

MDL-28599 textlib Separated collator to collatorlib with static methods, and added support for locale aware sorting of objects

Hopefully we now get the same results on all systems.

This may solve problems with encodings unsupported in iconv and random borked chars are ignored.

MDL-23899 fixed asort to modify parameter instead of returning array - it now matches standard asort()

AMOS BEGIN
  MOV [locale,core],[locale,core_langconfig]
  MOV [localewin,core],[localewin,core_langconfig]
  MOV [localewincharset,core],[localewincharset,core_langconfig]
  MOV [oldcharset,core],[oldcharset,core_langconfig]
AMOS END