Replace SGPlacementTrans usage with osg::PositionAttitueTransform.

Replace SGPlacementTrans usage with osg::PositionAttitueTransform.
Remove SGPlacementTrans.
Update build system.

Modified Files:
	SimGear.dsp projects/VC7.1/SimGear.vcproj
	projects/VC8/SimGear.vcproj simgear/scene/model/Makefile.am
	simgear/scene/model/placement.cxx
	simgear/scene/model/placement.hxx
	simgear/scene/tgdb/TileEntry.cxx
	simgear/scene/tgdb/TileEntry.hxx
Removed Files:
 	simgear/scene/model/placementtrans.cxx
 	simgear/scene/model/placementtrans.hxx