Streamline PHP patches

[assambar]

• Make the php 8.1 patch work (exclude fibers code or implement with asyncify)
• Check how to better integrate autotools changes
• Choose better ifdefs - wasm, wasi, add autoconf checks for headers/functions and use HAVE_XXX where applicable

[jedjones-uk]

As a long time PHP developer, I think it's important to implement the fibers code. It was a big deal them bringing it into PHP to begin with and having it solves the webserver problem in a way since it would allow the continued use of things like https://github.com/amphp and https://github.com/reactphp.

I think what you are doing here in general has huge potential for PHP but to pull people away from the standard approach it really needs to have an edge. I think providing an actual non-blocking-io runtime that works with the fibers would be huge as it is one of the biggest issues with PHP today and it's async story.

[ereslibre]

This is WIP at php/php-src#10457