Add support for hardware decryption ( CAM, part of linux-dvb )

Many dvb devices support hardware decryption ( CI ) for encrypted ( e.g. pay ) tv. In some countries almost all providers encrypt all channels and for some encryption types hardware decryption is the only possible / legal way to decrypt. Other apps like mythtv and kaffeine support this. It is part of linux-dvb and can be found in dvb_ca.h ( see http://linuxtv-dvb.sourcearchive.com/documentation/1.1.1/dvb__ca_8h-source.html ).