Add support for arbitrary HTTP methods

Hi internals, I want to bring here question about supporting custom http methods in built-in webserver with router script. The problem is that GET, POST are standard methods and they work fine, but for custom methods like XYZ_METHOD_ALSO_ALLOWED webserver responds with 501 Not Implemented. 501 ideally should never happen when router script is used, since it is up to router to decide whether it can handle the request or not. Initial bug report for additional info and references: https://bugs.php.net/bug.php?id=72619 Sample repository to reproduce an issue: https://github.com/nazar-pc/php-bug-72619 Christoph Michael Becker said on bug tracker that this kind of change will probably require an RFC, however for me this appears to be pretty minor change that can barely be a breaking change to someone and it should even be backported to 7.0/5.6 when/if implemented in 7.1. I do not code in C/C++, but I can prepare some PHPT tests for this feature if someone is willing to help here. -- Sincerely, Nazar Mokrynskyi