Reland: graphics: Use math.Ceil for the screen framebuffer size (#622)
Reland: graphics: Use math.Ceil for the screen framebuffer size (#622)

This is reland of 0b60471ac08215cd0ed47608fcc0fa1e00ffd162.

I thought this didn't take any effect, but I confirmed this
actually fixed (part of) the blinking-line problem on Xperia XZ.
This fixes the upper side thin line. I'm not sure this fixes the
lower side thin line, which is reported but I couldn't reproduce.

I expect this and e829e650f2903315c3e0796811c5b5cdaba9edb8 will
fix the reported problem, and I am going to confirm this.

hajimehoshi/ebiten,hajimehoshi/ebiten