1- Update the bullet source files
2- Update the visual studio project accordingly (e.g. add any new cpp files)
3- Apply the patches required:
4
5See https://github.com/libgdx/libgdx/commit/da30acc5b3521d0fda760ba765ae76a951bd41d7
6- Add a default ctor to btWheelInfo.h (around line 82): `btWheelInfo() {}`
7- Comment out `class btVehicleTuning;` in btRaycastVehicle.h ~22
8- Add ContactStartedCallback and ContactEndedCallback, based on http://www.bulletphysics.org/Bullet/phpBB3/viewtopic.php?t=7739&p=32470, as shown in https://github.com/libgdx/libgdx/commit/d492533c3ed9447560770a7482d32c2bfbae5df7:
9  btManifoldResult.cpp ~87:
10	bool isNewCollision = m_manifoldPtr->getNumContacts() == 0;
11  btManifoldResult.cpp ~154: 
12	if (gContactStartedCallback && isNewCollision)
13	{
14		gContactStartedCallback(m_manifoldPtr);
15	}
16  btPersistentManifold.cpp ~24:
17	ContactStartedCallback		gContactStartedCallback = 0;
18	ContactEndedCallback		gContactEndedCallback = 0;
19  btPersistentManifold.h ~31:
20	#ifndef SWIG
21	class btPersistentManifold;
22  btPersistentManifold.h ~36:
23	typedef void(*ContactStartedCallback)(btPersistentManifold* const &manifold);
24	typedef void(*ContactEndedCallback)(btPersistentManifold* const &manifold);
25  btPersistentManifold.h ~40:
26	extern ContactStartedCallback gContactStartedCallback;
27	extern ContactEndedCallback gContactEndedCallback;
28	#endif //SWIG
29  btPersistentManifold.h ~183:
30		if (gContactEndedCallback && m_cachedPoints == 0)
31		{
32			gContactEndedCallback(this);
33		}
34  btPersistentManifold.h ~242:
35		if (gContactEndedCallback && m_cachedPoints)
36		{
37			gContactEndedCallback(this);
38		}
39- Fix cast error for mingw: bDNA.cpp ~393+429 & bFile.cpp ~446+483: `nr= (long)*(intptr_t*)&cp;`
40- Disable SSE for IOS, in btScalar.h, around line 176, that starts with `#if (defined(__APPLE__) `...
41  btScalar.h ~177: Add: `#include <TargetConditionals.h>`
42  btScalar.h ~178: Modify the line to look `like: #if (defined (__i386__) || defined (__x86_64__)) && (!(TARGET_IPHONE_SIMULATOR))`
43  btScalar.h ~179+180+183: comment out `#define BT_USE_SIMD_VECTOR3` and `BT_USE_SSE` and `#define BT_USE_SSE_IN_API`
44