BUILD: cache: include tools.h in cache.c

cache.c uses a lot of functions from tools.h without including it.
diff --git a/src/cache.c b/src/cache.c
index a95abe5..bdb8258 100644
--- a/src/cache.c
+++ b/src/cache.c
@@ -32,6 +32,7 @@
 #include <haproxy/shctx.h>
 #include <haproxy/stream.h>
 #include <haproxy/stream_interface.h>
+#include <haproxy/tools.h>
 
 #define CACHE_FLT_F_IMPLICIT_DECL  0x00000001 /* The cache filtre was implicitly declared (ie without
 					       * the filter keyword) */