Added AMI 386DX and MR 386DX models (both based on OPTi 495 chipset). AMI 386DX supports external cache, useful for with prefetch emulation.

Also commit a few fixes required :
- Set EDX correctly on soft reset
- LOCK NOP is now treated as an illegal instruction
- Tweaks to FDC sense interrupt handling following FDC reset

src/x86seg.c

@@ -1603,6 +1603,7 @@ void pmodeint(int num, int soft)
                         pclog("Triple fault!\n");
 //                        output=1;
                         softresetx86();
+                        cpu_set_edx();
                 }
                 else if (num==0xD)
                 {