#62804 add information about parameter change in changelog

git-svn-id: https://svn.php.net/repository/phpdoc/en/trunk@331920 c90b9560-bf6c-de11-be94-00142212c4b1
Added ImagickPixel::isPixelSimilar
Added deprecated notes
Added setImageOpacity note

git-svn-id: https://svn.php.net/repository/phpdoc/en/trunk@331921 c90b9560-bf6c-de11-be94-00142212c4b1