Fix build with GCC-10.

Thanks-to: Walter Hüttenmeyer
Bug: https://bugs.gentoo.org/724988

--- a/src/minimizer.cc	2016-09-24 11:29:40.000000000 +0200
+++ b/src/minimizer.cc	2020-05-24 13:09:58.199170984 +0200
@@ -19,7 +19,7 @@
  */
 
 #include <gsl/gsl_errno.h>
-
+#include <limits>
 #include "minimizer.h"