Implemented preliminary S3 ViRGE 2D blitter emulation.

Misc ViRGE fixes.
Changes to memory mapping.
Changes to PCI handling.
Disabled 'AMI WinBIOS 486 PCI' due to incomplete chipset emulation.
Invalid GUS register reads no longer kill the emulator.

src/vid_ati28800.c

@@ -4,6 +4,7 @@
 #include "device.h"
 #include "io.h"
 #include "mem.h"
+#include "rom.h"
 #include "video.h"
 #include "vid_ati28800.h"
 #include "vid_ati_eeprom.h"
@@ -15,6 +16,8 @@ typedef struct ati28800_t
         svga_t svga;
         ati_eeprom_t eeprom;
         
+        rom_t bios_rom;
+        
         uint8_t regs[256];
         int index;
 } ati28800_t;
@@ -143,6 +146,8 @@ void *ati28800_init()
         ati28800_t *ati28800 = malloc(sizeof(ati28800_t));
         memset(ati28800, 0, sizeof(ati28800_t));
         
+        rom_init(&ati28800->bios_rom, "roms/bios.bin", 0xc0000, 0x8000, 0x7fff, 0, 0);
+        
         svga_init(&ati28800->svga, ati28800, 1 << 19, /*512kb*/
                    ati28800_recalctimings,
                    ati28800_in, ati28800_out,
@@ -158,6 +163,11 @@ void *ati28800_init()
         return ati28800;
 }
 
+static int ati28800_available()
+{
+        return rom_present("roms/bios.bin");
+}
+
 void ati28800_close(void *p)
 {
         ati28800_t *ati28800 = (ati28800_t *)p;
@@ -194,7 +204,7 @@ device_t ati28800_device =
         0,
         ati28800_init,
         ati28800_close,
-        NULL,
+        ati28800_available,
         ati28800_speed_changed,
         ati28800_force_redraw,
         ati28800_add_status_info