Fixed assertion that were broken with recent delayed header response.

Changed semantic of put_header_lines and add_header_lines,
Now the arguments are iterable of string (i.e the header line)

The previous features were not used, and were not well named.
So we removed them, and reused the names for adpated implementation.

library/server/wsf/src/implementation/wsf_wgi_delayed_header_response.e

@@ -14,7 +14,8 @@ inherit
 			put_string,
 			put_substring,
 			flush,
-			message_writable
+			message_writable,
+			message_committed
 		end
 
 	WSF_RESPONSE_EXPORTER
@@ -36,10 +37,10 @@ feature {NONE} -- Implementation
 
 	commit
 		do
-			Precursor
 			if not header_committed then
 				process_header
 			end
+			Precursor
 		end
 
 	process_header
@@ -65,6 +66,12 @@ feature -- Status report
 	message_writable: BOOLEAN = True
 			-- Can message be written?
 
+	message_committed: BOOLEAN
+			-- <Precursor>
+		do
+			Result := header_committed
+		end
+
 feature -- Output operation
 
 	put_character (c: CHARACTER_8)