fix compiler warnings in pvr.demo
add virtual destructors to some of the interfaces
fix compiler warnings in pvr.dvblink
fix compiler warnings in pvr.hts
fix compiler warnings in pvr.mediaportal.tvserver
fix compiler warnings in pvr.nextpvr
fix compiler warnings in pvr.njoy
fix compiler warnings in pvr.vdr.vnsi
fix compiler warnings in pvr.vuplus
fix compiler warnings in pvr.wmc
use correct type when comparing to npos