MINOR: lua: add AppletHTTP class and service

This class is used by Lua code for running as an applet called in HTTP mode
It defines also the associated lua service
diff --git a/include/types/applet.h b/include/types/applet.h
index 2254b0a..2e1626a 100644
--- a/include/types/applet.h
+++ b/include/types/applet.h
@@ -121,6 +121,13 @@
 			struct task *task;
 		} hlua_apptcp;
 		struct {
+			struct hlua hlua;
+			int left_bytes; /* The max amount of bytes that we can read. */
+			int flags;
+			int status;
+			struct task *task;
+		} hlua_apphttp;
+		struct {
 			struct dns_resolvers *ptr;
 		} resolvers;
 		struct {