First stage in refactoring Bullet: moved Bullet Collision and Dynamics and LinearMath into src folder, and all files in Collision Detection and Dynamics have bt prefix.

Made all buildsystems to work again (jam, msvc, cmake)

src/BulletCollision/CollisionDispatch/btUnionFind.cpp

@@ -0,0 +1,77 @@
+/*
+Bullet Continuous Collision Detection and Physics Library
+Copyright (c) 2003-2006 Erwin Coumans  http://continuousphysics.com/Bullet/
+
+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.
+*/
+
+#include "btUnionFind.h"
+#include <assert.h>
+#include <algorithm>
+
+
+
+UnionFind::~UnionFind()
+{
+	Free();
+
+}
+
+UnionFind::UnionFind()
+{ 
+
+}
+
+void	UnionFind::Allocate(int N)
+{
+	m_elements.resize(N);
+}
+void	UnionFind::Free()
+{
+	m_elements.clear();
+}
+
+
+void	UnionFind::reset(int N)
+{
+	Allocate(N);
+
+	for (int i = 0; i < N; i++) 
+	{ 
+		m_elements[i].m_id = i; m_elements[i].m_sz = 1; 
+	} 
+}
+
+bool UnionFindElementSortPredicate(const Element& lhs, const Element& rhs)
+{
+	return lhs.m_id < rhs.m_id;
+}
+
+
+///this is a special operation, destroying the content of UnionFind.
+///it sorts the elements, based on island id, in order to make it easy to iterate over islands
+void	UnionFind::sortIslands()
+{
+
+	//first store the original body index, and islandId
+	int numElements = m_elements.size();
+	
+	for (int i=0;i<numElements;i++)
+	{
+		m_elements[i].m_id = find(i);
+		m_elements[i].m_sz = i;
+	}
+	
+	 // Sort the vector using predicate and std::sort
+	  std::sort(m_elements.begin(), m_elements.end(), UnionFindElementSortPredicate);
+
+}
+