Notification of string changes

Author: dinhloc
MDL-61033 quiz: Editing a quiz while a preview is open
Editing a quiz while a preview is open in another browser tab can leads to a cryptic error that is hard to recover from


http://git.moodle.org/gw?p=moodle.git;a=commit;h=5d70a00dd8bbc03526a25bc0c5cff2a31c8f991a
http://github.com/moodle/moodle/commit/5d70a00dd8bbc03526a25bc0c5cff2a31c8f991a

+ 3.3 en [attempterrorinvalid,mod_quiz]
+ 3.3 en [attempterrorcontentchange,mod_quiz]
+ 3.3 en [attempterrorcontentchangeforuser,mod_quiz]