Bug: Missing includes in simpath.h

While porting my ai classes I noticed an error with
static GFXStateBlockRef smStateBlock;
static GFXVertexBufferHandle<GFXVertexPC> smVertexBuffer;
static GFXPrimitiveBufferHandle smPrimitiveBuffer;
in simpath.h on object Marker.

The missing includes are:

#ifndef _GFXSTATEBLOCK_H_
#include "gfx/gfxStateBlock.h"
#endif

#ifndef _GFXVERTEXBUFFER_H_
#include "gfx/gfxVertexBuffer.h"
#endif

Btw. it would be nice when the _SIGNAL_H_ flag would be renamed in core/util/tSignal.h, because this flag is the same as on unix signal.h, which would it make easier for future of linux/unix porting.