Notification of string changes

Author: Jun Pataleta
MDL-78983 core: Fix question mark icon direction flipping
This fixes the changes made in MDL-75047:
* Change `thisicondirection` langconfig string to a more specific one
like `questionicondirection`.
* Use existing direction string value `ltr` for the value of
`questionicondirection`. Also add a comment to at least provide some
form of documentation for it.
* Improve the logic for applying the horizontal flipping class for the
question icon:
- Check first if the icon is a question icon
- Flip the icon if `questionicondirection` is set to `rtl`.


http://git.moodle.org/gw?p=moodle.git;a=commit;h=b504d19c12f6723501dcb00cfefe682e9758538a
http://github.com/moodle/moodle/commit/b504d19c12f6723501dcb00cfefe682e9758538a

+ 4.1 en [questionicondirection,core_langconfig]
- 4.1 en [thisicondirection,core_langconfig]