Now that we don't have AC_CHECK_LIB(m, pow), the HAVE_LIBM symbol
disappears.  It wasn't used anywhere anyway...
diff --git a/config.h.in b/config.h.in
index 03a7fb0..0c95dd0 100644
--- a/config.h.in
+++ b/config.h.in
@@ -462,6 +462,3 @@
 
 /* Define if you have the ieee library (-lieee).  */
 #undef HAVE_LIBIEEE
-
-/* Define if you have the m library (-lm).  */
-#undef HAVE_LIBM