Windows builds of PHP 7.4+ use Visual Studio 2019

Hi, I like to inform you, that the official Windows builds of PHP 7.4 and master (available from windows.php.net; currently only snapshot builds, of course) are done with Visual Studio 2019. While it is still possible to build these PHP versions with Visual Studio 2017, this is no longer tested. This also means a small but important change, namely that we are no longer using the "vc" prefix (e.g. "vc14", "vc15") to refer to *new* Visual Studio versions, but rather "vs" (i.e. "vs16"). The detailed reasoning is explained in the post titled "Visual Studio 2019 Builds"[1]. Recent beta versions of the PHP SDK are supposed to fully support this naming change already (and particularly the renaming of the PHP_SDK_VC environment variable to PHP_SDK_VS). You may have to adapt custom tooling accordingly, though. Thanks, Christoph [1] <https://windows.php.net/>