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_vga.c

@@ -4,6 +4,7 @@
 #include "device.h"
 #include "io.h"
 #include "mem.h"
+#include "rom.h"
 #include "video.h"
 #include "vid_svga.h"
 #include "vid_vga.h"
@@ -11,6 +12,8 @@
 typedef struct vga_t
 {
         svga_t svga;
+        
+        rom_t bios_rom;
 } vga_t;
 
 void vga_out(uint16_t addr, uint8_t val, void *p)
@@ -78,6 +81,8 @@ void *vga_init()
         vga_t *vga = malloc(sizeof(vga_t));
         memset(vga, 0, sizeof(vga_t));
 
+        rom_init(&vga->bios_rom, "roms/ibm_vga.bin", 0xc0000, 0x8000, 0x7fff, 0, 0);
+
         svga_init(&vga->svga, vga, 1 << 18, /*256kb*/
                    NULL,
                    vga_in, vga_out,
@@ -91,6 +96,11 @@ void *vga_init()
         return vga;
 }
 
+static int vga_available()
+{
+        return rom_present("roms/ibm_vga.bin");
+}
+
 void vga_close(void *p)
 {
         vga_t *vga = (vga_t *)p;
@@ -127,7 +137,7 @@ device_t vga_device =
         DEVICE_NOT_WORKING,
         vga_init,
         vga_close,
-        NULL,
+        vga_available,
         vga_speed_changed,
         vga_force_redraw,
         vga_add_status_info