[ 1691402 ] Heighfield performance patch patch
[ 1691402 ] Heighfield performance patch patch

Fix two bug introduced in last patch and reported in mailing list :

- Ray segfault on tagential cases
- XZ oriented terrain that was letting object falling through and made the
reporter uses previous implementation.

git-svn-id: 83d585846b3bb6dc23aa7649400c5e2e04e3d09e@1175 685f7672-210f-0410-90b4-fe3ad19314fe

vancegroup-mirrors/open-dynamics-engine-svnmirror,vancegroup-mirrors/open-dynamics-engine-svnmirror,vancegroup-mirrors/open-dynamics-engine-svnmirror,vancegroup-mirrors/open-dynamics-engine-svnmirror,vancegroup-mirrors/open-dynamics-engine-svnmirror