changed: (almost) remove CStdString from CurlFile

one small use left, will be removed in an upcoming commit
changed: get rid of CStdString in CScraperUrl
changed: get rid of CStdString in CGUIDialogBoxBase
changed: get rid of CStdString in CGUIDialogSelect
changed: drop CStdString overload for StringUtils::Split
changed: get rid of CStdString in CUtil::CleanString
changed: get rid of CStdString in CCueDocument
changed: get rid of CStdString in CPlayListFactory
changed: get rid of CStdString in TuxBoxUtil
changed: (almost) get rid of CStdString in CGUIWindowVideoBase::AppendAndClearSearchItems

cast goes away in upcoming commit
changed: get rid of CStdString in CFileItem, CFileItemList, CGUIListItem
changed: get rid of CStdString in IMusicInfoTagLoader+implementations
changed: get rid of CStdString in CMusicFileDirectory+implementation
changed: get rid of CStdString in DVDDemuxers

some usage left in the ffmpeg one, will be removed in an upcoming commit
changed: get rid of CStdString in ICodec+implementations
changed: get rid of CStdString in paplayer's CodecFactory
changed: get rid of CStdString in CURL