Fixes #1142. CSecurityManager::computeHMAC() now has public accessor.
PHPDoc of the CSecurityManager::computeHMAC() has been enhanced.
Merge branch 'master' of github.com:yiisoft/yii into fixes-1142
UPGRADE note for #2249 and #1142. Related to the CSecurityManager::computeHMAC().
Merge pull request #2249 from resurtm/fixes-1142

Fixes #1142. CSecurityManager::computeHMAC() has been made public.