include/smb_macros.h: Don't round up an allocation if the size is zero.

include/smb_macros.h: Don't round up an allocation if the size is zero.
"One of these locks is not like the others... One of these locks is not
quite the same" :-). When is a zero timeout lock not zero ? When it's
being processed by Windows 2000 of course.. This code change, ugly though
it is - completely fixes the foxpro/access multi-user file system database
problems that people have been having. I used a *wonderful* test program
donated by "Gerald Drouillard" <gerald@drouillard.ca> which allowed me
to completely reproduce this problem, and to finally determine the correct
fix. This also explains why Windows 2000 is *so slow* when responding to
the smbtorture lock tests. I *love* it when all these things come together
and finally make sense :-).
Jeremy.
(This used to be commit 8aa9860ea2ea7f5aed4b6aa12794fffdfa81b0d0)