Add the old Bullet 2.x obsolete demos, and CMake buildsystem files, and gradually move them to newer Bullet 3.x structure

Use statically linked freeglut, instead of dynamic glut for the obsolete Bullet 2.x demos
Add the 'reset' method to b3GpuDynamicsWorld, and use it in the BasicGpuDemo (pretty slow in debug mode, use release mode)
Don't crash in btCollisionWorld, if there is no collision dispatcher

ObsoleteDemos/ConcaveDemo/Jamfile

@@ -0,0 +1,3 @@
+SubDir TOP Demos ConcaveDemo ;
+
+BulletDemo ConcaveDemo : [ Wildcard *.h *.cpp  ] ;