If a thread doesn't terminate, we log that but not longer proceed

(because it could hang later still).

Also logging to stderr as well to make sure one sees it.

Also adding code to the ASCII writer to catch termination
inconsistencies.

src/logging/writers/Ascii.h

@@ -40,6 +40,7 @@ private:
 	FILE* file;
 	string fname;
 	ODesc desc;
+	bool ascii_done;
 
 	// Options set from the script-level.
 	bool output_to_stdout;