MINOR: lua: add runtime execution context

The functions added permits to execute the LUA stack execution in
HAProxy. It provides all the runtie environment and initialise the
main LUA stack.
diff --git a/include/proto/hlua.h b/include/proto/hlua.h
index c69210e..20c329b 100644
--- a/include/proto/hlua.h
+++ b/include/proto/hlua.h
@@ -6,6 +6,8 @@
 #include <types/hlua.h>
 
 /* Lua HAProxy integration functions. */
+int hlua_ctx_init(struct hlua *lua, struct task *task);
+void hlua_ctx_destroy(struct hlua *lua);
 void hlua_init();
 
 #endif /* _PROTO_HLUA_H */