remove constraints/rigid bodies from dynamics world in btBulletWorldImporter

Thanks to vicariousentertainment, see http://code.google.com/p/dynamica/issues/detail?id=16
Enable SIMD OpenCL cloth solver by default
enable keyboard 'up' for Windows (non-Glut) version

Demos/DX11ClothDemo/cloth_renderer.cpp

@@ -38,7 +38,7 @@ class btDX11SIMDAwareSoftBodySolver;
 #include "BulletSoftBody/btSoftBodyRigidBodyCollisionConfiguration.h"
 
 #define USE_SIMDAWARE_SOLVER
-#define USE_GPU_SOLVER
+//#define USE_GPU_SOLVER
 #define USE_GPU_COPY
 const int numFlags = 5;
 const int clothWidth = 40;