Add support for `htmlspecialchars` features

[alexanderteplov]

1. Starting from version 5.4 PHP supports predefined constant ENT_HTML5 used as a flag for htmlspecialchars. This constant is currently unsupported by the compiler, given the following error: Compilation error at stage: Inline defines pass, gen by inline-defines-usages.cpp:38.

2. From the same (or close) version PHP supports 4 arguments for htmlspecialchars (currently only 2 supported). See php.net/manual/en/function.htmlspecialchars.php

It would be nice of you to support both of these things to allow such constructions: htmlspecialchars($string, ENT_HTML5, 'CP-1251', false).

The example of code above is essential to support such languages as Chinese or Japanese for elephize for WEB. Contact me if you need more details.