MDL-40260 block_course_overview: prevent MNET courses from being dimmed
MDL-40585 backup: cache XML parent paths

For $this->groupedpaths, using a key is faster as there is
no need to do in_array searches.

Parent cache allows dirname calls to be substantially reduced.
2048 was chosen as a cache size as this class operates on chunks
of the restore at a time, 8k questions produces a parent cache of
about 500 paths and uses 300K of memory.  Scaling up to 2048 will
use about 1.2M of RAM for really large restores.  This is acceptable
for the 48% function call reduction and the 10% runtime improvement
seen.
MDL-40584 backup: Query db once per category in precheck

The cache is function local and testing against a large database
indicates 10k questions is a large category.  Restore already
uses MEMORY_EXTRA and that will have enough space for the couple
of megabtyes a local sql hash will introduce.
MDL-40680 store_memcached: fix serialiser options

* Use correct lang string for SERIALIZER_IGBINARY
* Use PARAM_INT for the parameter
MDL-37333 theme: Fix 'Clear theme caches' redirect.
MDL-40626 gradebook: Prevent incorrect override with multiline feedback

The quick grading option doesn't allow mutliline editing.
MDL-38867 remove Google spell checking option
MDL-20609 quiz tables: improve layout for long cell contents.

By allowing more wrapping.
MDL-40480 tablelib: specify charset in XHMTL downloads.

Thanks to Jürgen Zimmer for the suggestion.
MDL-40785 question instances report: ignore subquestions

We should not count subquestions of cloze questions (parent != 0) but we
do want to count random questions (parent = id).
MDL-40679 mark zlib extension as recommended
MDL-40700 cache: Validate memcache key prefix field
MDL-40700 cache: memcache and memcached stores now allow alphanumext prefixes
MDL-40174 navigation: don't remove active root nodes without children
Merge branch 'wip-MDL-37333_M24' of git://github.com/gjb2048/moodle into MOODLE_24_STABLE
Merge branch 'wip-MDL-40174-m24' of git://github.com/samhemelryk/moodle into MOODLE_24_STABLE
Merge branch 'm24_MDL-40260' of git://github.com/danmarsden/moodle into MOODLE_24_STABLE
MDL-40260 Course overview: code tidy for previous commit

Moving this check inside the following if makes it clear which code
branch it applies to.
Merge branch 'w30_MDL-38867_m24_gspell' of https://github.com/skodak/moodle into MOODLE_24_STABLE
Merge branch 'MDL-40626-24' of git://github.com/danpoltawski/moodle into MOODLE_24_STABLE