BUILD: spoe: flt_spoe.c needs tools.h

It uses many functions declared there but used to inherit it through others.
diff --git a/src/flt_spoe.c b/src/flt_spoe.c
index 7749cc9..a68f7b9 100644
--- a/src/flt_spoe.c
+++ b/src/flt_spoe.c
@@ -36,6 +36,7 @@
 #include <haproxy/tcp_rules.h>
 #include <haproxy/thread.h>
 #include <haproxy/time.h>
+#include <haproxy/tools.h>
 #include <haproxy/vars.h>