Function            scrbuff - calculate size of screen buffer

  Syntax              #include <video.h>
                      scrbuff(l,t,r,b)

  Prototype in        video.h

  Remarks             this is really just a define to calculate the size
                      of a buffer need by Borland's gettext() and
                      puttext() functions.

  Return value        returns the number of bytes needed to store a
                      segment of screen from (l,t) to (r,b), with
                      attributes.

  See also            video.h