\x1b7 and \x1b8 is not reachable in ansiparser

The two cases [here](https://github.com/pcman-bbs/pcman.js/blob/95f4b786a4dba97b0375456cdb1f787cb4d3eb18/lib/ansiparser.js#L205-L212) are not reachable due to if statement in [here](https://github.com/pcman-bbs/pcman.js/blob/95f4b786a4dba97b0375456cdb1f787cb4d3eb18/lib/ansiparser.js#L193).
