Add bullet >= 281 support (no fracturing).
Add missing cassert includes.
Delete duplicate tracksurface.h.
Fix performance testing.
GUI: Use opacity instead of alpha (html/css like).
Translate bool guioption strings.
Support multiple cars replay (single race), bump replay version number. Single race gui has to be updated.
Remove unused (and immediate mode) GRAPHICS_GL2::DrawBox.
Cache selected texture unit, saves about 30% call time per simple single textured object.  GLSTATEMANAGER doesn't take texture unit into account, only enables/disables first unit, should be fixed eventually.
Style: Spelling fix in comment.
Remove unused REDNER_INPUT_SCENE::SelectAppropriateShader and redundant GetCull check.
RENDER_INPUT_SCENE move DrawVertexArray code into a function, move GL_LINE_SMOOTH setup to BeginScene.
HUD strings translation hack, should be rewritten as guipage.
HUD: Add spacers as leading/trailing spaces are not supported by current multi-language implementation.
Introduce update.cars/tracks gui options to signal available updates number.
Load road patches in VDrift coord system to get rid of patch-world transforms.
Use gui font for hud text.
Fix car place calculation.
HUD: Add info box for lap, place, score.
Backport sim auto clutch logic.