[dcl.dcl] Change example for static_assert (#1923)

Author: jensmaurer

source/declarations.tex

@@ -174,7 +174,7 @@
 \begin{example}
 
 \begin{codeblock}
-static_assert(char(-1) < 0, "this library requires plain 'char' to be signed");
+static_assert(sizeof(int) == sizeof(void*), "wrong pointer size");
 \end{codeblock}\end{example}
 
 \pnum