More GJK degeneracy fixes, thanks Jacob Langford for the feedback:

http://code.google.com/p/bullet/issues/detail?id=250

Added missing files for Maya Dynamica plugin
Thanks Herbert Law for the patch, and damrit and others for the report
http://code.google.com/p/bullet/issues/detail?id=231

Fix btQuaternion shortestArcQuat, thanks Stan Melax for original fix and shogun for reminder
http://bulletphysics.com/Bullet/phpBB3/viewtopic.php?f=9&t=1989

Implemented btDiscreteDynamicsWorld::removeCollisionObject (and btSoftBodyDynamicsWorld) to avoid
crashes. Thanks Jacob Langford for bringing that up.

Minor sphere-debug drawing issue (spheres were drawn inside-out (wrong face winding)

Extras/MayaPlugin/constraint/bt_constraint.h

@@ -0,0 +1,54 @@
+/*
+Bullet Continuous Collision Detection and Physics Library Maya Plugin
+Copyright (c) 2008 Walt Disney Studios
+ 
+This software is provided 'as-is', without any express or implied warranty.
+In no event will the authors be held liable for any damages arising
+from the use of this software.
+Permission is granted to anyone to use this software for any purpose,
+including commercial applications, and to alter it and redistribute it freely,
+subject to the following restrictions:
+ 
+1. The origin of this software must not be misrepresented; you must
+not claim that you wrote the original software. If you use this
+software in a product, an acknowledgment in the product documentation
+would be appreciated but is not required.
+2. Altered source versions must be plainly marked as such, and must
+not be misrepresented as being the original software.
+3. This notice may not be removed or altered from any source distribution.
+ 
+Written by: Nicola Candussi <nicola@fluidinteractive.com>
+*/
+
+//bt_constraint.h
+
+#ifndef DYN_BT_CONSTRAINT_H
+#define DYN_BT_CONSTRAINT_H
+
+#include "btBulletCollisionCommon.h"
+#include "btBulletDynamicsCommon.h"
+#include "shared_ptr.h"
+
+class bt_constraint_t 
+{
+public:
+
+protected:
+    friend class bt_solver_t;
+
+    bt_constraint_t() { }
+
+    btTypedConstraint* constraint()                     { return m_constraint.get(); }
+    void set_constraint(btTypedConstraint *constraint)  { return m_constraint.reset(constraint); }
+	virtual void update_constraint() = 0;
+
+public:
+    friend class bt_rigid_body_t;
+
+    virtual ~bt_constraint_t() { }
+
+protected:
+    shared_ptr<btTypedConstraint> m_constraint; 
+};
+
+#endif