Fix problems detected as dead assignment warning by clang scan-build.

Wrong assignment by shutdown result hides the real error code
of NewRequestHandler() in ssdp_device.c.
Fix return code description of NewRequestHandler().
Handle return code from ithread_create in sample applications.
Remove unused assignments.

upnp/src/genlib/net/http/httpreadwrite.c

@@ -1206,7 +1206,6 @@ static int ReadResponseLineAndHeaders(
 			return num_read;
 		}
 	}
-	done = 0;
 	status = parser_parse_headers(parser);
 	if ((status == (parse_status_t)PARSE_OK) &&
 		(parser->position == (parser_pos_t)POS_ENTITY))