File filtering.

(Appendix 21)

 There is a possibility to filter files that are uploaded to the BBS.  This
is done by a F_FILTER program.

 The F_FILTER may also be created as a DLL.  Both for WinFBB and DosFBB (!!).
The filter must be installed in the path (\FBB\BIN) of Dos.

 If the F_FILTER exists, the temporary file is no longer deleted by WinFBB 
(unless return value from F_FILTER is 0), the filter must decide what to do. 

 F_FILTER receives as parameter a file in which are given information such 
as asked filename and label. If F_FILTER returns 0, then the file is normally
recorded (and the temporary file is deleted), else nothing is done by FBB. 
The text returned by F_FILTER will be sent to the user. So an archive may be 
compressed, scanned, and a report may be sent to the user. This can be done 
in real time or delayed.