2.87
Split Bullet/src/LinearMath/btSerializer.cpp into btSerializer64.cpp to make it easier to rebuild serialization structure. Add several MSVC optimization flags to cmake. Bump up VERSION because serialization format changed Expose btScalar& jointMaxForce, btScalar& jointMaxVelocity to 'getJointInfo2' API, add backwards compatibility to examples\Importers\ImportURDFDemo\URDFImporterInterface::getJointInfo.
add the 'extras' and Bullet 2 tests, to make it easier to create a new intermediate release
fix in structure alignment of btMultiBodyLinkDoubleData and btMultiBodyDoubleData causing serialization issue in URDF/SDF loading in double-precision mode on Windows 32bit. (it was fine on Mac/Linux 64bit) bump serialization version to 2.85, as we change the file format fix in name clash in makesdna.cpp -> intptr_t is already defined.