[ODE] GIMPACT merged to trunk

[Jason Perkins]

That was messy, but GIMPACT is now merged with the ODE trunk. For the
time being, I have added the GIMPACT sources directly to the ODE
repository. If Francisco sets up a separate repository later we can
link there.

For the moment, you will need Premake (http://premake.sf.net/) to
build with GIMPACT. In the future, once we've cleaned up all the
#if... blocks you will be able to flip a switch in <config.h> but
until then. In the ode/build directory run

  premake --with-gimpact --with-tests --target xxx

...where "xxx" is one of vs2005, vs2003, vs2002, gnu, or cb-gcc (type
`premake --help` for help). That will create a solution ode.sln (or
makefile or whatever) you can use to build ode and the tests. Works
for Visual Studio, might have issues elsewhere, YMMV.

A big question for Francisco: at collision_trimesh_gimpact.cpp(474)
you call FetchTriangle() and use the results, but you never
implemented FetchTriangle(). I filled in with an assert for now.

A couple of notes: I only applied the changes directly related to
GIMPACT support. So the trimesh/box "null normal" fix and the
autodisable fix were not applied. Those should be submitted and
considered separately.

You now need to call dInitODE() on startup - this has been added to
all of the tests.

test_trimesh fails with GIMPACT, apparently because the triangle
winding is wrong. We need to fix either GIMPACT or OPCODE so that it
works consistently.

I think that's it for now. Give it a try and let me know what you think.

Jason