Fix lost MouseButtonUp events when releasing mouse outside window (Linux/X11)

[TheRedDeveloper]

Problem

On Linux (X11), macroquad was unconditionally calling miniquad::window::set_cursor_grab(false) every frame in Stage::update when the cursor wasn't explicitly grabbed.

This is problematic because miniquad's X11 implementation calls XUngrabPointer whenever set_cursor_grab is called. This cancels X11's "implicit passive grab" where it automatically routes events to the window when a mouse button is held down, even if the cursor leaves the window.

As a result, dragging the mouse outside the window and releasing it would result in the application never receiving the MouseButtonUp event, getting stuck in a "pressed" state.

Solution

• I modified Context to track previous_cursor_grabbed state.
• If cursor_grabbed is true, we continue to call set_cursor_grab(true) every frame (maintaining existing functionality).
• If cursor_grabbed is false, we only call set_cursor_grab(false) once, when the state transitions from true to false.

After all, the set_cursor_grab(true) needs to happen every frame to assert that the cursor is grabbed, but set_cursor_grab(false) needs to happen only once.

Hope this helps!