Use arrays for wmEvent coordinates, this quiets warnings with GCC11. - `x, y` -> `xy`. - `prevx, prevy` -> `prev_xy`. - `prevclickx, prevclicky` -> `prev_click_xy`. There is still some cleanup such as using `copy_v2_v2_int()`, this can be done separately. Reviewed By: campbellbarton, Severin Ref D12901