Author: Marina Glancy
MDL-49003 login: prevent signup when user is logged in
http://git.moodle.org/gw?p=moodle.git;a=commit;h=0a976df90c79a997fa9d259d0945f43386d17d20
http://github.com/moodle/moodle/commit/0a976df90c79a997fa9d259d0945f43386d17d20
+ 2.8 en [cannotsignup,core_error]