Merging r6551 through r6553 from branch releases/1.8 to trunk

All about bounds checks and preventing buffer overruns in b3d and obj files based on sfan5 patches for Minetest


git-svn-id: svn://svn.code.sf.net/p/irrlicht/code/trunk@6554 dfc29bdd-3216-0410-991c-e03cc46cb475

source/Irrlicht/SB3DStructs.h

@@ -12,6 +12,7 @@
 #define SB3DSTRUCTS_H
 
 #include "SMaterial.h"
+#include "irrMath.h"
 
 namespace irr {
 namespace scene {
@@ -27,6 +28,7 @@ struct SB3dChunk
 	SB3dChunk(const SB3dChunkHeader& header, long sp)
 		: length(header.size+8), startposition(sp)
 	{
+		length = core::max_(length, 8);
 		name[0]=header.name[0];
 		name[1]=header.name[1];
 		name[2]=header.name[2];