We fix (hopefully) all instances of: * <https://docs.microsoft.com/en-us/cpp/error-messages/compiler-warnings/compiler-warning-level-1-c4005> * <https://docs.microsoft.com/en-us/cpp/error-messages/compiler-warnings/compiler-warning-level-1-c4024> * <https://docs.microsoft.com/en-us/cpp/error-messages/compiler-warnings/compiler-warning-level-1-c4028> * <https://docs.microsoft.com/en-us/cpp/error-messages/compiler-warnings/compiler-warning-level-1-c4047> * <https://docs.microsoft.com/en-us/cpp/error-messages/compiler-warnings/compiler-warning-level-1-c4087> * <https://docs.microsoft.com/en-us/cpp/error-messages/compiler-warnings/compiler-warning-level-1-c4090> * <https://docs.microsoft.com/en-us/cpp/error-messages/compiler-warnings/compiler-warning-level-1-c4273> * <https://docs.microsoft.com/en-us/cpp/error-messages/compiler-warnings/compiler-warning-level-1-c4312> `zend_llist_add_element()` and `zend_llist_prepend_element()` now explicitly expect a *const* pointer. We use the macro `ZEND_VOIDP()` instead of a `(void*)` cast to suppress C4090; this should prevent accidential removal of the cast by clarifying the intention, and makes it easier to remove the casts if the issue[1] will be resolved sometime. [1] <https://developercommunity.visualstudio.com/content/problem/390711/c-compiler-incorrect-propagation-of-const-qualifie.html>
