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/scat.c

@@ -208,6 +208,7 @@ void scat_write(uint16_t port, uint8_t val, void *priv)
                 if ((~scat_port_92 & val) & 1)
                 {
                          softresetx86();
+                        cpu_set_edx();
                 }
                 scat_port_92 = val;
                 break;