[expr.const] Add cross-reference for 'constant initialization'.

Author: jensmaurer

source/expressions.tex

@@ -7315,7 +7315,8 @@
 to determine whether it is satisfied\iref{temp.constr.atomic}, or
 \item the initializer of a variable
 that is usable in constant expressions or
-has constant initialization.\footnote{Testing this condition
+has constant initialization\iref{basic.start.static}.%
+\footnote{Testing this condition
 may involve a trial evaluation of its initializer as described above.}
 \begin{example}
 \begin{codeblock}