Building ext/intl fails with MSVC /std:c11 (#17179)

A previous fix to be able to build C++ extensions with MSVC[1], was
based on the assumption that `max_align_t` would be defined in stddef.h
on Windows.  That was plain wrong; there is no such typedef (or macro).

Thus we revert that fix, and instead make an exception for Windows,
where we always use the fallback definition, which should work fine on
Windows.

[1] <ab449a7>

Author: cmb69

Zend/zend_portability.h

@@ -789,13 +789,9 @@ extern "C++" {
 # define ZEND_STATIC_ASSERT(c, m)
 #endif
 
-#if (defined(__STDC_VERSION__) && __STDC_VERSION__ >= 201112L) /* C11 */
+#if ((defined(__STDC_VERSION__) && __STDC_VERSION__ >= 201112L) /* C11 */ \
+  || (defined(__cplusplus) && __cplusplus >= 201103L) /* C++11 */) && !defined(ZEND_WIN32)
 typedef max_align_t zend_max_align_t;
-#elif (defined(__cplusplus) && __cplusplus >= 201103L) /* C++11 */
-extern "C++" {
-# include <cstddef>
-}
-typedef std::max_align_t zend_max_align_t;
 #else
 typedef union {
 	char c;