Add support for part/triangle id for GIMPACT.

Thanks Alex Silverman:
http://www.bulletphysics.com/Bullet/phpBB3/viewtopic.php?f=9&t=2032

Extras/GIMPACT/include/GIMPACT/Bullet/btGImpactCollisionAlgorithm.h

@@ -256,9 +256,39 @@ public:
 
 
 
-//!@}
-
-
+		/// Accessor/Mutator pairs for Part and triangleID
+    void 	setFace0(int value) 
+    { 
+    	m_triface0 = value; 
+    }
+    int getFace0() 
+    { 
+    	return m_triface0; 
+    }
+    void setFace1(int value) 
+    { 
+    	m_triface1 = value; 
+    }
+    int getFace1() 
+    { 
+    	return m_triface1; 
+    }
+    void setPart0(int value) 
+    { 
+    	m_part0 = value; 
+    }
+    int getPart0() 
+    { 
+    	return m_part0; 
+    }
+    void setPart1(int value) 
+    { 
+    	m_part1 = value; 
+		}
+    int getPart1() 
+    { 
+    	return m_part1; 
+    }
 
 };
 

Extras/GIMPACT/src/Bullet/btGImpactCollisionAlgorithm.cpp

@@ -783,6 +783,8 @@ public:
 	{
 		btTriangleShapeEx tri1(triangle[0],triangle[1],triangle[2]);
 		tri1.setMargin(margin);
+        algorithm->setPart1(partId);
+        algorithm->setFace1(triangleIndex);
 		algorithm->gimpact_vs_shape(
 							body0,body1,gimpactshape0,&tri1,swapped);
 	}