5ff4243 added auto-capture for tracking mouse motion while buttons are pressed (enabled by default). It looks like this could interfere with applications that call SDL_CaptureMouse() themselves, most notably when the mouse button up event after clicking unexpectedly releases their mouse capture.

It seems like we might need some internal mouse capture function that knows the difference between auto-capture and manual capture to ensure that the external SDL_CaptureMouse() API still behaves as expected for existing applications. Auto-capture also causes observable changes to the window flags (setting SDL_WINDOW_MOUSE_CAPTURE), which we might want to also suppress for application compatibility reasons.