Grib vertaxis order

This is an update I apply before incorporating 4.3 builds into our application.  The fix restores the vertAxis ordering used in 4.2 builds.  It appears that Grib1Rectilyser is trying to sort records according to vert axis ordering, but makes a sign error when deciding whether to reverse the order for positive down axes.  

I'm happy continuing to apply the path with every update, but think the fix might be helpful to the rest of the community.