-and the ability to compile and link the specified @var{testcode}. If found,
-it sets and AC_SUBSTs @code{HAVE_LIB<@var{NAME}>=yes} and the
-@code{LIB<@var{NAME}>} and @code{LTLIB<@var{NAME}>} variables (with
+and the ability to compile and link the specified @var{testcode}. The
+@var{missing-message} defaults to @code{no} and may contain additional hints
+for the user. If found, it sets and AC_SUBSTs @code{HAVE_LIB<@var{NAME}>=yes}
+and the @code{LIB<@var{NAME}>} and @code{LTLIB<@var{NAME}>} variables (with