Reset EGA/VGA character scanline counter when hitting split screen start line.

src/vid_svga.c

@@ -585,6 +585,7 @@ void svga_poll(void *p)
                 {
 //                        pclog("VC split\n");
                         svga->ma = svga->maback = 0;
+                        svga->sc = 0;
                         if (svga->attrregs[0x10] & 0x20) 
                                 svga->scrollcache = 0;
                 }