Author: Huong Nguyen
MDL-53368 core_auth: Implement reCaptcha on login page
http://git.moodle.org/gw?p=moodle.git;a=commit;h=0cd29afb6ff8c6764f9ac2e69dde499dda4fc483
http://github.com/moodle/moodle/commit/0cd29afb6ff8c6764f9ac2e69dde499dda4fc483
+ 4.3 en [auth_loginrecaptcha,core_auth]
+ 4.3 en [auth_loginrecaptcha_desc,core_auth]