fix compile issue(s) in BT_USE_DOUBLE_PRECISION mode

src/BulletDynamics/ConstraintSolver/btSliderConstraint.h

@@ -25,6 +25,8 @@ TODO:
 #ifndef BT_SLIDER_CONSTRAINT_H
 #define BT_SLIDER_CONSTRAINT_H
 
+#include "LinearMath/btScalar.h"//for BT_USE_DOUBLE_PRECISION
+
 #ifdef BT_USE_DOUBLE_PRECISION
 #define btSliderConstraintData2		btSliderConstraintDoubleData
 #define btSliderConstraintDataName  "btSliderConstraintDoubleData"

src/LinearMath/btScalar.h

@@ -17,6 +17,7 @@ subject to the following restrictions:
 #ifndef BT_SCALAR_H
 #define BT_SCALAR_H
 
+
 #ifdef BT_MANAGED_CODE
 //Aligned data types not supported in managed code
 #pragma unmanaged