revert quickSort change in commit http://code.google.com/p/bullet/source/detail?r=2527 and fix the underlying sort issue

in VoronoiFractureDemo (store intermediate values in memory to avoid problems)
@todo: rewrite the island management to avoid sort for better performance
Thanks to Peter Kyme for the report, fixes Issue 607

src/LinearMath/btAlignedObjectArray.h

@@ -313,46 +313,34 @@ protected:
 				}
 		};
 	
-		template <typename L>
-		int partition (const L& CompareFunc, int lo, int hi, int pivotIndex)
-		{
-			if (pivotIndex != lo)
-				swap (lo, pivotIndex);
-
-			pivotIndex = lo;
-			lo++;
-			while (lo <= hi)
-			{
-				//if (m_data[low] <= m_data[pivotIndex]) -> we don't have a <= so we use !(b<a) as a<=b 
-				if (!CompareFunc(m_data[pivotIndex],m_data[lo]))
-					lo++;
-				else if (CompareFunc(m_data[pivotIndex],m_data[hi]))
-					hi--;
-				else
-					swap(lo,hi);
-			}
-			if (hi != pivotIndex)
-				swap(pivotIndex, hi);
-			return hi;
-		}
 
 		template <typename L>
 		void quickSortInternal(const L& CompareFunc,int lo, int hi)
 		{
-			if (lo>=hi)
-				return;
-			int pivotIndex = (lo+hi)/2;
-			pivotIndex = partition(CompareFunc,lo,hi,pivotIndex);
-			
-			//  recursion, exclude the pivot
-			if (lo<pivotIndex) 
-			{
-				quickSortInternal( CompareFunc, lo, pivotIndex-1);
-			}
-			if (pivotIndex<hi) 
-			{
-				quickSortInternal( CompareFunc, pivotIndex+1, hi);
-			}
+		//  lo is the lower index, hi is the upper index
+		//  of the region of array a that is to be sorted
+			int i=lo, j=hi;
+			T x=m_data[(lo+hi)/2];
+
+			//  partition
+			do
+			{    
+				while (CompareFunc(m_data[i],x)) 
+					i++; 
+				while (CompareFunc(x,m_data[j])) 
+					j--;
+				if (i<=j)
+				{
+					swap(i,j);
+					i++; j--;
+				}
+			} while (i<=j);
+
+			//  recursion
+			if (lo<j) 
+				quickSortInternal( CompareFunc, lo, j);
+			if (i<hi) 
+				quickSortInternal( CompareFunc, i, hi);
 		}