Draw window only when both LCDC.0 and LCDC.5 are enabled

[rhysd]

Window should be rendered only when LCDC.0 and LCDC.5 are enabled. But mooneye-gb checks only LCDC.5. This PR fixes the point.

PanDocs: https://gbdev.io/pandocs/LCDC.html#ff40---lcdc-lcd-control-rw

[rhysd]

The diff may look a bit complicated, but actually this PR simply moves the if clause for rendering window into the if clause for rendering background so that the window can be rendered only when the background is rendered. (Please check 'Hide whitespace' diff setting in the review page)