Choose the best vsync method for the user, instead of asking them to
frustratingly try every one of the options to see what works.
With this commit, the `vsync` option will take only a boolean value.
Signed-off-by: Yuxuan Shui <yshuiv7@gmail.com>
Moved:
* Blur kernel related functions to kernel.c
* Vsync related functions to vsync.c
* paint related functions to render.c
This will make the `split-backend` branch easier to rebase.
Signed-off-by: Yuxuan Shui <yshuiv7@gmail.com>