Merged revisions 1972:2004 from 1.5 branch, except for some revisions which seemed to be merged already. MD2 loader updated, terrain node fixed, opengl texture handling fixed.

git-svn-id: svn://svn.code.sf.net/p/irrlicht/code/trunk@2005 dfc29bdd-3216-0410-991c-e03cc46cb475