[php-src] PR #25126: Fix FFI calling conventions inside nested declarators

Pull Request: https://github.com/php/php-src/pull/25126 Author: nicolas-grekas FFI ignores the calling convention in void (__stdcall *f)(void). That's how Windows headers declare callbacks, for example PAPCFUNC. On x86, such a callback is created as cdecl. The callback then doesn't pop its argument and the stdcall caller crashes. That's why sleep_alertable_win32.phpt from #24399 crashes on nightly (#25125 changes the test). In a parameter or a type name, as in FFI::type('void (__stdcall *)(int)'), the same syntax fails with "Unsupported type specifier combination". A convention that the platform doesn't support is now rejected inside the parentheses too, like it already is before them. For example, void (__stdcall *f)(void) now throws on x64. I updated ffi_parser.c by hand, the same way LLK generates the other cases.