changed: get rid of CStdString in StereoscopicsManager

the casts are a temporary measure (will be removed in
an upcoming commit)
changed: get rid of CStdString in CLangInfo
changed: get rid of CStdString in CLocalizeStrings
changed: make CAdvancedSettings::m_musicItemSeparator a std::string
changed: get rid of CStdString in CSong
changed: get rid of CStdString in XBMC_MD5
changed: get rid of CStdString in CGUIKeyboardFactory
changed: get rid of CStdString in a couple of URIUtils methods
changed: get rid of CStdString in CMusicDatabase::GetArtistPath
changed: get rid of CStdString in CArtist
changed: get rid of CStdString in URIUtils::RemoveExtension
changed: get rid of CStdString in Xcddb
changed: get rid of CStdString in CDatabase
changed: get rid of CStdString in CUtil::GetQualifiedFilename
changed: get rid of CStdString in StringUtils::RemoveCRLF
changed: get rid of CStdString in CPlayList (and its children)
changed: get rid of CStdString in CDatabaseQueryRule(Combination) plus children
changed: get rid of CStdString in CGUIWindow::OnEditChanged
changed: get rid of CStdString in CSmartPlayList
changed: get rid of CStdString in CMusicDatabase