Closes dunglas/frankenphp#682.

The extension causes issues with FrankenPHP because it isn't setting the SA_ONSTACK signal handler flag, which is mandatory for use in processes started by Go (as well as many other runtimes), and a best practice anyway.

PHP itself now uses SA_ONSTACK, see this patch for the full rationale: php/php-src#9597

Also, the extension uses signal() is discouraged:

WARNING: the behavior of signal() varies across UNIX versions, and has also varied historically across different versions of Linux.
Avoid its use: use sigaction(2) instead.

https://www.man7.org/linux/man-pages/man2/signal.2.html

This patch sets SA_ONSTACK and switch from signal() to sigaction().

I didn't change the global behavior, but totally ignoring SIGPIPE would also be fine IMHO. Servers should ignore it.