-dnl the ability to compile and link the specified testcode. If found, it
-dnl sets and AC_SUBSTs HAVE_LIB${NAME}=yes and the LIB${NAME} and
-dnl LTLIB${NAME} variables and augments the CPPFLAGS variable, and
+dnl the ability to compile and link the specified testcode. The missing-message
+dnl defaults to 'no' and may contain additional hints for the user.
+dnl If found, it sets and AC_SUBSTs HAVE_LIB${NAME}=yes and the LIB${NAME}
+dnl and LTLIB${NAME} variables and augments the CPPFLAGS variable, and