[php-src] PR #23753: Fix GH-23752: Restore GCC diagnostic state around global registers

Pull Request: https://github.com/php/php-src/pull/23753 Author: yqtian-se The global-register declarations need a local -Wvolatile-register-var exception, but the closing #pragma GCC diagnostic warning sets a new warning state instead of restoring the build's command-line policy. GCC diagnostic pragmas override command-line options, and warning explicitly downgrades this diagnostic even when the caller selected -Werror. Consequently, the current blocks violate either caller choice: - under -Wno-volatile-register-var, PHP re-enables a warning the caller disabled; - under -Werror=volatile-register-var, PHP downgrades the caller's requested error to a warning, allowing compilation to continue. The blocks are near the start of source files containing 5,733 and 1,327 lines, so this changed state covers most of both translation units. This patch uses #pragma GCC diagnostic push and pop around the three declarations. PHP's required declarations remain suppressed, while the exact prior state resumes immediately afterward. Validation on x86-64 Linux with GCC 11.4: - configured PHP-8.4 with --disable-all --enable-opcache --enable-opcache-jit and confirmed HAVE_GCC_GLOBAL_REGS=1; - compiled the real Zend/zend_execute.lo and ext/opcache/jit/zend_jit_vm_helpers.lo objects successfully; - compiled wrappers containing each complete source file followed by a valid %r13 global-register warning oracle; - with -Wno-volatile-register-var, both wrappers exited 0 with no diagnostics; - with -Werror=volatile-register-var, both wrappers failed only at the post-source oracle, confirming that the caller's error state was restored. No PHPT is included because this is compile-time diagnostic state, not PHP runtime behavior. I found no current endogenous later trigger in either translation unit, so this is not presented as a current default-build failure. The reproduced failure is the loss of the build's diagnostic policy, including the silent downgrade of an explicitly requested error. Fixes #23752