fixed hhvm build.

Fixes #5494: Added support for specifying a menu header as a configuration array in `yii\bootstrap\Dropdown`

Fixes #5070: Gii controller generator should use controller class name instead of controller ID to specify new controller

show PHP extension version

fixes #5503

fixes #6263 and has no problem with PHP Bug:

> it is a PHP bug: https://bugs.php.net/bug.php?id=45543
> Fixed in this commit: php/php-src@22dba2f#diff-7b738accc3d60f74c259da18588ddc5dL2996
>
> Fixed in PHP >5.4.26 and >5.5.10. http://3v4l.org/mlZX7

Fixes #5627: Added `yii cache/flush-schema` console command to flush DB schema cache of a given database connection

fixes #5448

fixes #6164

Fixes #4823 and #6005: `yii message` accuracy and error handling were improved by using PHP tokenizer instead of regular expressions. Removed eval() as well.

fixes #5683

Fixes #4643: Extra options specified in `yii\widgets\Breadcrumbs::links` will be treated as HTML attributes for the generated hyperlinks

return value would not be a valid array when json encoded after unlink().

fixes #6065

fixes #4745

Fixed `yii\sphinx\QueryBuilder` does not support comparison operators (>,<,>= etc) in where specification