ICL_LANGUAGE_CODE related support

Problem: ICL_LANGUAGE_CODE or wpml_current_language filter which is the best paractice

Solution: Using *ICL_LANGUAGE_CODE* constant or *wpml_current_language* API is fine. But a best practice is to use the API(*wpml_current_language*) because of the following reasons.

1) If something is changed in the future like the name of the *icl_language_code* your code may fail. The API should either return a result or return a result and deprecation notice

2) It depends on where and how you are using it. Using it via the API ensures that it will be called on time with the proper value inside

Relevant Documentation: https://wpml.org/wpml-hook/wpml_current_language/