[ODE] Proposal: Change Heightfield Origin

[David Walters]

> Sorry, you're right. I realize a lot more data is in double precision than I suspected

Hi, I've made a patch to add single and double precision paths through
the code, so that it's decoupled from the ODE build precision. However
I'm having trouble commiting it to sourceforge. I've sent the patch
file to Jason and hopefully he'll have better luck with SVN than I'm
having...

As for the origin change, it's clear that boths ways have their merits
and supporters... worse is that it's really not something that I think
should be optional at run time because that's just gonna cause some
horrible support requests.

Maybe a compromise is to use an internal #define in heightfield.cpp to
revert to the original code for those who prefer the existing
orientation... I guess as you can't please everyone with one solution,
a well documented build option is the best way of dealing with this?

Regards,
Dave.