#6218 - applying hotfix for `iconv.internal_encoding` deprecation

See https://wiki.php.net/rfc/default_encoding

 > PHP 5.6 and master, introduce new php.ini setting. Old iconv.*/mbstring.* php.ini parameters will be removed for master PHP6. Use of iconv.*/mbstring.* php.ini parameters raise E_DEPRECATED for 5.6 and up.
Merge pull request #6219 from Ocramius/hotfix/#6218-iconv-internal-encoding-deprecated-in-php-5.6

#6218 - applying hotfix for `iconv.internal_encoding` deprecation
Merge branch 'hotfix/6219'

Close #6219