MDL-38102 lib: Check for null return value from password_hash function call
MDL-38480_m Fix for messy usage of language strings in block course overview
MDL-39399 theme: Missing expand/collapse icon in clean
MDL-39399 theme: RTL styles for collapse/expand in forms
MDL-39435 feedback: Fix missing calls to setType
MDL-38714 Lesson module: add setType for hidden and text inputs
MDL-38500 repository: Instance names must be unique
MDL-38315 Completion: Bugs with 'locked' status in activity form
MDL-39448 MUC: Memcache configurable key names
MDL-39452 Library: html_writer::attribute unnecessary is_array check
MDL-32913 core_grade:made it more obvious when the gradebook is broken due to a broken calculation
MDL-38717: Lesson mod: fixed behat script to accomodate the fix of settype()
MDL-36223 Assign: User outline report grade display

Use str_long_grade for user outline report because it handles scales and
no grade.

Thanks to Jean-Daniel Descoteaux for suggesting this fix.
MDL-39442 Do not use native rename() when moving folders

The native rename() function does not support moving folders
cross-device. See https://bugs.php.net/bug.php?id=54097 for details. So
instead of trying to move the whole tree, the new installer's method
moves files recursively one by one.

This is consistent with what mdeploy.php already does.
MDL-38979 Add lang menu to empty custommenu

Show custom menu even when no custom menu items if lang menu needs
to be shown.
MDL-39388 bootstrapbase: Add bootstrap tab renderer

This adds a renderer that outputs standard bootstrap HTML for tabs,
deletes styles that were previously required to make Moodle tab HTML
superficially resemble Bootstrap, and tweak the responsive code that
makes tabs stack on phones to account for the change too.
MDL-39290 Collapsible editor tab needs some mouse-over CSS
MDL-39472 MUC: Improve parse_key performance
MDL-39445 get_plugin_list clean_param use is slow

get_plugin_list was calling clean_param($pluginname, PARAM_PLUGIN) a
lot (600+ times per page), and that is much slower than you would guess.
A specific function for this case, (which we then also use from
clean_param) is a performance win.
MDL-39446 calculated qtype: make answer formula input bigger

This makes it easier for teachers editing questions.