Two minor fixes: 1. Put integral_constant conversion to integral in even without constexpr support. 2. Add ios_base to <iosfwd>. The latter is being tracked by LWG 2026.

llvm-svn: 123080

libcxx/include/iosfwd

@@ -92,6 +92,8 @@ typedef fpos<char_traits<wchar_t>::state_type> wstreampos;
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
+class ios_base;
+
 template<class _CharT>  struct _LIBCPP_VISIBLE char_traits;
 template<class _Tp>     class _LIBCPP_VISIBLE allocator;
 

libcxx/include/type_traits

@@ -165,10 +165,11 @@ struct _LIBCPP_VISIBLE integral_constant
     static constexpr _Tp      value = __v;
     typedef _Tp               value_type;
     typedef integral_constant type;
-#ifndef _LIBCPP_HAS_NO_CONSTEXPR
     _LIBCPP_INLINE_VISIBILITY
-    constexpr operator value_type() {return value;}
+#ifndef _LIBCPP_HAS_NO_CONSTEXPR
+    constexpr
 #endif
+         operator value_type() const {return value;}
 };
 
 template <class _Tp, _Tp __v>