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/386.c

@@ -290,6 +290,7 @@ opcodestart:
                                 {
                                         cpu_state.abrt = 0;
                                         softresetx86();
+                                        cpu_set_edx();
                                         pclog("Triple fault - reset\n");
                                 }
                         }