MDL-39028 fix sqlsrv concat type conversion
MDL-39023 Make get_language_dependencies() aware of circular dependency risk

The patch reimplements the core_string_manager::get_language_dependencies()
so that potentially mis-configured language packs with circular
dependencies or self dependency do not make the site unavailable.
Unit tests for the expected behaviour are added.
MDL-38999 timezones: add some TZ/stamps know to be problematic to tests.
Merge branch 'MDL-39023-parentlang' of git://github.com/mudrd8mz/moodle
MDL 38508 JavaScript: Split out AJAX and non-AJAX help

We need to keep these two separate as scripts which define AJAX_SCRIPT
before loading config.php will use a different default renderer and will
return appropriate exceptions which can be parsed by M.core.exception and
M.core.ajaxException correctly.

This also addresses an issue whereby a missing heading could break the
tooltip.
MDL-39038 nasty workaround for Oracle NULL concats
MDL-39027 make sure sqlsrv does not return non-string data types
Merge branch 'MDL-38849' of git://github.com/timhunt/moodle
Merge branch 'MDL-38907-master' of git://github.com/damyon/moodle
Merge branch 'MDL-38744-master' of git://github.com/danpoltawski/moodle
Merge branch 'w14_MDL-34222_m25_simplepie131' of git://github.com/skodak/moodle
MDL-34222 simplepie: fix permissions.
Merge branch 'w14_MDL-38786_m25_yui391' of git://github.com/skodak/moodle
Merge branch 'MDL-38912' of git://github.com/timhunt/moodle
Merge branch 'MDL-38618_master' of git://github.com/dmonllao/moodle
Merge branch 'w14_MDL-39022_m25_mssqlconcat' of git://github.com/skodak/moodle
Merge branch 'w14_MDL-39024_m25_mssqlseek' of git://github.com/skodak/moodle
MDL-38792 Update question/type in-line comments to codechecker standards

Correct bad formated infiles in question/type directories
Merge branch 'w14_MDL-39019_m25_mssqldatatype' of git://github.com/skodak/moodle
MDL-38442 navigation: set_expansion_limit now only hides structural nodes