Demul v0.7 alpha 201215

Dreamcast/Naomi 1 + 2/Atomiswave/Hikaru/Cave CV1000/Gaelco 模擬器 Demul 再度更新，內容如下 :

quick follow-up
- implemented disk swap functionality (D2, Skies of Arcadia, etc)

http://forum.emu-russia.net/viewtopic.php?f=25&t=503&sid=e211a4933eaa4c7fc17a6f54ee15565e&start=160