[C] Fix unwanted point moveage in VM

[Aidan Kehoe]

 Ar an chéad lá is fiche de mí Méan Fómhair, scríobh Stephen J. Turnbull: 

 > Aidan Kehoe writes:
 > 
 >  > It should be possible to avoid this in VM. AIUI it’s a result of
 >  > doing coding system and base64, quoted-printable decoding on
 >  > displayed text, which will always cause a redisplay flash if the
 >  > relevant text is being shown.  (Text is inserted, more text is
 >  > deleted). It would make more sense to do all the decoding somewhere
 >  > that's not being redisplayed, and only show the text when the
 >  > decoding is finished.
 > 
 > I guess you could double buffer, have one buffer for the current view
 > (or preview) and another where the work is being done.  Is that what
 > you have in mind?

Yeah. I’ve experimented a little but haven’t yet got it to work. 

-- 
On the quay of the little Black Sea port, where the rescued pair came once
more into contact with civilization, Dobrinton was bitten by a dog which was
assumed to be mad, though it may only have been indiscriminating. (Saki)