Video related changes:

IBM/ATI 8514/A side:
Made mode switches more immediate when actually switching from VGA to 8514/A and viceversa.

Tseng ET4000AX/W32 series side:
Actually use bit 2 of index 0x3f for the horizontal blank start bit 8 instead of bit 4 (horizontal retrace start), fixes skew issues with the et4000w32i rev B. card with resolutions like 1024x768 at 15 or 16bpp and others.

src/video/vid_8514a.c

@@ -4454,7 +4454,7 @@ ibm8514_init(const device_t *info)
     }
 #endif
 
-    timer_add(&svga->timer8514, ibm8514_poll, svga, 0);
+    timer_add(&svga->timer8514, ibm8514_poll, svga, 1);
 
     return svga;
 }