[DVB-T Scans] Reverted as there's a C++ code error that prevents it from being build. So reverted: Scan both DVB-T/T2 when 'system' is not specified in terrestrial.xml. And, eDVBscan: add sanitycheck on m_ch_current. Requested by Abu Baniaz. Credit OpenPLi (pieterg, 24/7/2014). (reverse-merged from commit 8584ddd275bf219f4cdeb775b600356d77ace483)