The maximum alignment of std::aligned_storage applies to all Windows compilers

[rnk]

Summary

According to Clang's sources, the maximum supported storage alignment is a
property of the COFF object file format. Fixes building libc++ <type_traits>
with Clang on Windows.

[compnerd]

Yeah, this is a COFF limitation. Its unfortunate we don't have a better way to detect COFF targets.

[Eugene.Zelenko]

Looks like patch was not committed.

[mclow.lists]

I guess this is OK. I'd rather not have naked _WIN32 references outside of <__config>, but this is not the first one.

[mclow.lists]

This duplicates @D25053, and I've landed this change as revision 283621.

include/type_traits

 _CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x40);
 _CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x80);
 _CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x100);
 _CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x200);
 _CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x400);
 _CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x800);
 _CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x1000);
 _CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x2000);
-// MSDN says that MSVC does not support alignment beyond 8192 (=0x2000)
-#if !defined(_LIBCPP_MSVC)
+// PE COFF does not support alignment beyond 8192 (=0x2000)
+#if !defined(_WIN32)
 _CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x4000);
-#endif // !_LIBCPP_MSVC
+#endif // !_WIN32
 
 #undef _CREATE_ALIGNED_STORAGE_SPECIALIZATION
 
 #ifndef _LIBCPP_HAS_NO_VARIADICS
 
 // aligned_union
 
 template <size_t _I0, size_t ..._In>