BUG/MEDIUM: lua: sample fetches based on response doesn't work

The direction (request or response) is not propagated in the
sample fecthes called throught Lua. This patch adds the direction
status in some structs (hlua_txn and hlua_smp) to make sure that
the sample fetches will be called with all the information.

The converters can not access to a TXN object, so there are not
impacted the direction. However, the samples used as input of the
Lua converter wrapper are initiliazed with the direction. Thereby,
the struct smp stay consistent.
[wt: needs to be backported to 1.6]
diff --git a/include/types/hlua.h b/include/types/hlua.h
index 48f7487..a9b6498 100644
--- a/include/types/hlua.h
+++ b/include/types/hlua.h
@@ -100,6 +100,7 @@
 struct hlua_txn {
 	struct stream *s;
 	struct proxy *p;
+	int dir;                /* SMP_OPT_DIR_{REQ,RES} */
 };
 
 /* This struct contains the applet context. */
@@ -114,6 +115,7 @@
 	struct stream *s;
 	struct proxy *p;
 	int stringsafe;
+	int dir;                /* SMP_OPT_DIR_{REQ,RES} */
 };
 
 /* This struct contains data used with sleep functions. */