configure: dismiss libutil.h

Recent versions of libc on Linux (Debian Testing) create lots of
compile warnings about direct usage of libutil.h
diff --git a/configure.ac b/configure.ac
index adcd8d2..75f99a6 100755
--- a/configure.ac
+++ b/configure.ac
@@ -395,7 +395,7 @@
 dnl -------------------------
 AC_CHECK_HEADERS([stropts.h sys/ksym.h sys/times.h sys/select.h \
 	sys/types.h linux/version.h netdb.h asm/types.h \
-	sys/param.h limits.h signal.h libutil.h \
+	sys/param.h limits.h signal.h \
 	sys/socket.h netinet/in.h time.h sys/time.h])
 
 dnl Utility macro to avoid retyping includes all the time
diff --git a/lib/zebra.h b/lib/zebra.h
index 6d19910..c4c69d3 100644
--- a/lib/zebra.h
+++ b/lib/zebra.h
@@ -237,10 +237,6 @@
 #define UINT32_MAX	(4294967295U)
 #endif
 
-#ifdef HAVE_LIBUTIL_H
-#include <libutil.h>
-#endif /* HAVE_LIBUTIL_H */
-
 #ifdef HAVE_GLIBC_BACKTRACE
 #include <execinfo.h>
 #endif /* HAVE_GLIBC_BACKTRACE */