Apply blanking extensions to more SVGA cards.

* Fix duplicated logic in vid_svga.c
* Voodoo 3/Banshee emulation now has blanking extensions applied
* S3 ViRGE and Matrox video cards as well
* Tseng ET4000-series cards as well
* Fix off-by-one error in vid_cl54xx.c

Trident cards are yet to be investigated. XGA and 8514/A are yet to be made blanking extensions compliant. Mach64, Paradise/WDC and OAK OTI cards remain as-is for now.

src/video/vid_et4000.c

@@ -613,6 +613,8 @@ et4000_recalctimings(svga_t *svga)
         svga->rowoffset = 0x100;
     if (svga->crtc[0x3f] & 1)
         svga->htotal += 256;
+    if (svga->crtc[0x3f] & 0x04)
+        svga->hblankstart += 0x100;
     if (svga->attrregs[0x16] & 0x20)
         svga->hdisp <<= 1;