Separator drifts on repeated resize

[Christopher Beland]

In GNU Emacs 20.7.1 (i686-pc-linux-gnu, X toolkit)
 of Tue May 15 2001 on snuggle.mit.edu
configured using `configure  --with-x-toolkit --sharedstatedir=/var/tmp 
--with-pop --with-hesiod --with-kerberos'

> Please describe exactly what actions triggered the bug
> and the precise symptoms of the bug:

Normally, if I do M-x 2, the separator between the two buffers splits
screen real estate exactly 50/50, i.e., it's right in the vertical
middle of the screen.

When I do the following:
 - Start Emacs (in X)
 - M-x 2
 - Grab the bottom of the window and slowly drag it up and down repeatedly

...my window manager, namely Sawfish 0.37.3, redraws the contents of
the Emacs window several times a second.  For some reason - probably
some sort of rounding error - the separator bar drifts.  When I'm done
resizing the window, one of the buffers might end up being very much
smaller than the other.  I would expect Emacs to retain the same
proportional division of space between buffers no matter how the
window is resized.