[dcl.fct] Add missing period after last sentence in example. (#2494)

source/declarations.tex

@@ -3272,7 +3272,7 @@
 However, the first argument must be of a type
 that can be converted to a
 \tcode{const}
-\tcode{char*}
+\tcode{char*}.
 \end{example}
 \begin{note}
 The standard header