PPageFileInfo: Try to request the filename and size from the filter first.

Allows RARFileSource to show the real filename and size of the file being played.
WebClientSocket: Try to request filename and size from the filter.
MainFrm: Use general GetFileName() to decide the window title and don't rely on the parameter.
MainFrm: Use general GetFileName() for OSD first play message and favourite creation.
SaveDlg: Allow extraction of RAR files using RFS.