2.83
add the 'extras' and Bullet 2 tests, to make it easier to create a new intermediate release
fix HACD crash, thanks to gjaegy See https://github.com/bulletphysics/bullet3/pull/277
add .bullet extension in File/Open on Mac add importer support for FIXED_CONSTRAINT_TYPE, to be replaced by btGeneric6DofSpring2Constraint btFixedConstraint now derives from btGeneric6DofSpring2Constraint
rename ObsoleteDemos back to Demos fix some relative path issues for loading assets