minimal libcpp: Un-11-ify cstddef

Don't expose C++11 APIs unless we're building for that platform

Signed-off-by: Andy Ross <andyross@google.com>

squashme cdecl

lib/cpp/minimal/include/cstddef

@@ -18,8 +18,10 @@
 namespace std {
 	using ::ptrdiff_t;
 	using ::size_t;
+#if __cplusplus >= 201103L
 	using ::max_align_t;
 	using nullptr_t = decltype(nullptr);
+#endif
 }
 
 #endif /* ZEPHYR_SUBSYS_CPP_INCLUDE_CSTDDEF_ */