Add a note to the definition of literal type to indicate that it is not

a guarantee that such an object can be created in a constant expression.

Wording from John Spicer / CWG.

Addresses NB GB 68 (C++17 CD).

Author: zygoloid

source/basic.tex

@@ -3645,6 +3645,14 @@
 of non-volatile literal types.
 \end{itemize}
 \end{itemize}
+\begin{note}
+A literal type is one for which
+it might be possible to create an object
+within a constant expression.
+It is not a guarantee that it is possible to create such an object,
+nor is it a guarantee that any object of that type
+will usable in a constant expression.
+\end{note}
 
 \pnum
 \indextext{layout-compatible type}%