Added missing export defs for some Bullet classes.

panda/src/bullet/bulletAllHitsRayResult.h

@@ -28,7 +28,7 @@
 //       Class : BulletRayHit
 // Description : 
 ////////////////////////////////////////////////////////////////////
-struct BulletRayHit {
+struct EXPCL_PANDABULLET BulletRayHit {
 
 PUBLISHED:
   INLINE static BulletRayHit empty();

panda/src/bullet/bulletSoftBodyNode.h

@@ -38,7 +38,7 @@ class BulletSoftBodyWorldInfo;
 //       Class : BulletSoftBodyNodeElement
 // Description : 
 ////////////////////////////////////////////////////////////////////
-class BulletSoftBodyNodeElement {
+class EXPCL_PANDABULLET BulletSoftBodyNodeElement {
 
 PUBLISHED:
   INLINE ~BulletSoftBodyNodeElement();

panda/src/bullet/bulletVehicle.h

@@ -31,7 +31,7 @@ class BulletWheel;
 //       Class : BulletVehicleTuning
 // Description : 
 ////////////////////////////////////////////////////////////////////
-class BulletVehicleTuning {
+class EXPCL_PANDABULLET BulletVehicleTuning {
 
 PUBLISHED:
   INLINE void set_suspension_stiffness(PN_stdfloat value);