Add Mouse_motion_debounce configuration variable
In the SDL2 backend, mouse motion can cause jerky movement and lag. For instance,
https://pulkomandy.tk/projects/GrafX2/ticket/136
As related in that ticket, changing Merge_movement
doesn't work.
This patch adds a Mouse_motion_debounce
configuration option that can remedy this issue by debouncing the processing of mouse motion events.
(To test this patch, build with the SDL2 backend, verify the lag when using the brush selector or circle tools, and then add Mouse_motion_debounce = 20
to your gfx2.ini
file)