[MINOR] store HTTP error messages into a chunk array

HTTP error messages were all specific cases handled by an IF.
Now they are all in an array so that it will be easier to add
new ones. Also, the return functions now use chunks as inputs
so that it should be easier to provide alternative return
messages if needed.
diff --git a/include/types/httperr.h b/include/types/httperr.h
index c594048..c466328 100644
--- a/include/types/httperr.h
+++ b/include/types/httperr.h
@@ -32,6 +32,19 @@
 #define DATA_ST_INIT	0
 #define DATA_ST_DATA	1
 
+/*
+ * All implemented return codes
+ */
+enum {
+	HTTP_ERR_400 = 0,
+	HTTP_ERR_403,
+	HTTP_ERR_408,
+	HTTP_ERR_500,
+	HTTP_ERR_502,
+	HTTP_ERR_503,
+	HTTP_ERR_504,
+	HTTP_ERR_SIZE
+};
 
 
 #endif /* _TYPES_HTTPERR_H */