added basic serialization for several constraints including btPoint2PointConstraint, btHingeConstraint, btSliderConstraint, btConeTwistConstraint, btGeneric6DofConstraint

(no motor support or advanced settings yet)
added btStaticPlaneShape serialization
Added toggle in cmake for BenchmarksDemo to enable/disable graphics rendering

src/LinearMath/btSerializer.h

@@ -72,6 +72,7 @@ public:
 
 #define BT_COLLISIONOBJECT_CODE MAKE_ID('C','O','B','J')
 #define BT_RIGIDBODY_CODE		MAKE_ID('R','B','D','Y')
+#define BT_CONSTRAINT_CODE		MAKE_ID('C','O','N','S')
 #define BT_BOXSHAPE_CODE		MAKE_ID('B','O','X','S')
 #define BT_SHAPE_CODE			MAKE_ID('S','H','A','P')
 #define BT_ARRAY_CODE			MAKE_ID('A','R','A','Y')
@@ -268,18 +269,18 @@ public:
 
 			if (VOID_IS_8)
 			{
-//#if _WIN64
+#if _WIN64
 				initDNA((const char*)sBulletDNAstr64,sBulletDNAlen64);
-//#else
-//				btAssert(0);
-//#endif
+#else
+				btAssert(0);
+#endif
 			} else
 			{
-//#ifndef _WIN64
+#ifndef _WIN64
 				initDNA((const char*)sBulletDNAstr,sBulletDNAlen);
-//#else
-//				btAssert(0);
-//#endif
+#else
+				btAssert(0);
+#endif
 			}
 
 		}