Author: Andrew Davis
MDL-28568 message: added a warning message when the user is about to message someone who cant reply
http://git.moodle.org/gw?p=moodle.git;a=commit;h=36e22a820c1a22abd656ec0d4221982bafdd6e5a
http://github.com/moodle/moodle/commit/36e22a820c1a22abd656ec0d4221982bafdd6e5a
+ 2.3 en [messagingblockednoncontact,core_message]
+ 2.3 en [userisblockingyounoncontact,core_message]