Changes
/* UNDONE : old screen effect (called also sometimes scanline) */
[http://www.cpcwiki.eu/forum/games/everything-looks-better-in-scanlines!/msg119154/#msg119154 Everything looks better in scanlines!]
Problem : in CoreAmstrad, output VGA resolution is already at top (1 pixel is 1 pixel), CRT 768x288 is rendered into a 800x600 VGA, so I can't add an filter (without destroying VGA signal). CoreAmstrad is not using a simple 384x288 scandoubler like other core in VGA, but a VRAM.
=== DONE : Monochrome option ===
