MDL-42582 Availability: Restriction display incorrect for multi-para Labels

When a label has multiple paragraphs, its name (converted to plain text)
contains a line feed. Due to an error in regular expressions that don't
accept the line feed, this caused incorrect display on the course page
when that label is shown as a requirement for accessing another activity.
MDL-33536 navigation: hide hidden categories from the navbar
MDL-42723: Hide and handle LDAP error when user not in context being checked

MDL-41304 only fixed the case when 'Search subcontext' is enabled. We need to
fix the case when it's not enabled too.

While silencing errors with an @ should be avoided if possible, there's no
other way to prevent the warnings in this case.
MDL-42672 blocks: warnings on /mod/xxx/index.php for frontpage course
MDL-42808 library: Google API was resetting the timezone
MDL-38574 qtype chooser: quick fix to make it fit on-screen.

MDL-32729 will provide a better fix for this, but we may as well apply
this quick fix on stable branches.
MDL-42598 quiz variant randomisation not random enough.

A student would get the same question variants (for example for a
calculated question) on their first attempt at both copies of a
duplicated quiz.
Automatically generated installer lang files
MDL-42790 essay attempt on last: fix plain reponse mode

Plain responses, without files, were getting messed up by the
fix for MDL-39980. Something that looked like an HTML comment was being
appended.

This fix works by avoiding appending anything if there are no files. The
new unit test (which was failing before I fixed the code) confirms that
this works. The other tests should be enough to verify that there are no
regressions.
MDL-42839 MUC: Memcache server configuration too sensitive to whitespace
Merge branch 'wip-MDL-42672-m25' of git://github.com/marinaglancy/moodle into MOODLE_25_STABLE
Merge branch 'wip_25_mdl-42723' of https://github.com/iarenaza/moodle into MOODLE_25_STABLE
Merge branch 'MDL-38574_25' of git://github.com/timhunt/moodle into MOODLE_25_STABLE
Merge branch 'MDL-42839-m25' of git://github.com/sammarshallou/moodle into MOODLE_25_STABLE
Merge branch 'MDL-42790_25' of git://github.com/timhunt/moodle into MOODLE_25_STABLE
MDL-38574 recompiled moodle.css in bootstrapbase
Automatically generated installer lang files
MDL-33536 Navigation: Add missing require_once for safety.
Merge branch 'MDL-33536-25' of git://github.com/damyon/moodle into MOODLE_25_STABLE
Merge branch 'MDL-42598_25' of git://github.com/timhunt/moodle into MOODLE_25_STABLE