MDL-39335: add an ord() unicode analog to textlib.
MDL-38896 theme_bootstrapbase: Abbreviated weekdays in calendar/renderer.php + added @media css rule for calendar view.
MDL-39377 Increase padding for grouped field labels in question types
MDL-39378 s(): fix bad hex regex
MDL-39378 Improve s() performance.

These changes give about a 10% speed-up in this function. The significant changes are:
1. Simplify the if logic to remove unnecssary cases.
2. Dont pass default argument values to htmlspecialchars, just using the
   defaults is faster.
3. I can confirm that /i regex is faster than the equivalent regex without the i.

I also added more unit tests to test the edge cases.
MDL-39336 do not print debug output before finishing installation
MDL-39336 some themes may use $SITE->shortname in page layout before installation finishes
MDL-39336 fix incorrect use on join() in simple theme
MDL-39364 theme_clean: Changed 'simple' to 'clean'.
MDL-39292 use consistent iconsmall in enrol instances UI
MDL-39174 fix phpdocs packages in themes
MDL-39386 fix phpdocs packages in enrol
MDL-39387 fix /auth phpdocs
MDL-39387 normalise MOODLE_INTERNAL
MDL-39371 add dependency of clean theme on bootstrapbase
MDL-39077 get_max_upload_sizes always include option for 0

Always include an option for 0 in the list of bytes even if sitebytes is not set.
MDL-39077 fix regression in previous commit, the limit should be always included in maxbytes
MDL-39077 add more unit tests for get_max_upload_sizes()
MDL-39389 add databasemeta cache to ms/oci drivers
MDL-39389 add databasemeta cache to pdo_sqlite

Done in a separate commit, coz this driver is not
truly supported, but considering it as a reference
for people developing drivers... it's better to
have it supporting the databasemeta cache.