Set transaction enabled flag default to TRUE
DB_driver's trans_complete exception fix
Issue #2086 Session_cookie's _update_db not guaranteed to update
Merge pull request #2267 from dionysiosarvanitis/fix/_update_db

Issue #2086 Session_cookie's _update_db not guaranteed to update
Merge pull request #2265 from dionysiosarvanitis/fix/trans_enabled

Set transaction enabled flag default to TRUE
Remove CI_DB_pdo_driver::

Improving on PR #2265, the property is inherited with the same value and doesn't need to be set.
Update user_guide_src/source/tutorial/news_section.rst

Clarified a part of the tutorial so it's obvious the code should be replaced/update rather than added.
Fix Session tests
[ci skip] Remove a changelog line for a non-existent change
Manually apply PR #2234
Disable autoloader call from class_exists() occurences to improve performance

Note: The Driver libary tests seem to depend on that, so one occurence in CI_Loader is left until we resolve that.
DB_result tests seem to also depend on autoloading via the class_exists() checks ...
Fix #2273
Merge pull request #2266 from dionysiosarvanitis/fix/trans_complete

DB_driver's trans_complete exception fix
Merge pull request #2274 from ckdarby/patch-1

Fix #2273
Add CI_Utf8::convert_to_utf8() test
Some miscellaneous tests
CI_Output [set/append/get]_output() tests