constexpr applied to <array>.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@160564 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/include/array b/include/array
index c11f4bd..029bfd0 100644
--- a/include/array
+++ b/include/array
@@ -55,7 +55,7 @@
     // capacity:
     constexpr size_type size() const noexcept;
     constexpr size_type max_size() const noexcept;
-    bool empty() const noexcept;
+    constexpr bool empty() const noexcept;
 
     // element access:
     reference operator[](size_type n);
@@ -173,11 +173,11 @@
 
     // capacity:
     _LIBCPP_INLINE_VISIBILITY
-    /*constexpr*/ size_type size() const _NOEXCEPT {return _Size;}
+    _LIBCPP_CONSTEXPR size_type size() const _NOEXCEPT {return _Size;}
     _LIBCPP_INLINE_VISIBILITY
-    /*constexpr*/ size_type max_size() const _NOEXCEPT {return _Size;}
+    _LIBCPP_CONSTEXPR size_type max_size() const _NOEXCEPT {return _Size;}
     _LIBCPP_INLINE_VISIBILITY
-    bool empty() const _NOEXCEPT {return _Size == 0;}
+    _LIBCPP_CONSTEXPR bool empty() const _NOEXCEPT {return _Size == 0;}
 
     // element access:
     _LIBCPP_INLINE_VISIBILITY reference operator[](size_type __n)             {return __elems_[__n];}