Squashed 'extensions/AccountCaptcha/' content from commit eddd4bc

git-subtree-dir: extensions/AccountCaptcha
git-subtree-split: eddd4bc4f2703e1ebe76787aad9309bc2acce3ec
Add AccountCaptcha

Merge commit '72882a08af4b36ea593f39b849ce5055bf6fe77a' as 'extensions/AccountCaptcha'