setTexture functions for single textures (more or less the usual case) IRenderTarget no longer need memory allocations
on each call.
Also calling IRenderTarget::setTexture with a nullpointer no longer sets a rendertarget with an array which contains a single nullpointer but clears the array instead.
git-svn-id: svn://svn.code.sf.net/p/irrlicht/code/trunk@6243 dfc29bdd-3216-0410-991c-e03cc46cb475
Still can't decide on fixing/leaving function names... brr
git-svn-id: svn://svn.code.sf.net/p/irrlicht/code/trunk@6241 dfc29bdd-3216-0410-991c-e03cc46cb475
