Various 486 improvements

- Added SL-Enhanced versions of Intel 486 CPUs and Enhanced AMD Am486DX2/DX4 CPUs
- Cleaned up the 486 CPU types and updated intel_4x0.c to reflect this
- Fixed some incorrect EDX reset and CPUID values
- Blacklisted non-SMM capable 486 CPUs on the Soyo 4SA2 motherboard
- Merged the non-OverDrive and OverDrive Intel DX4s because of further research confirming them to be functionally identical
- Removed SMM support on early 486 CPUs

src/machine/machine.c

@@ -81,7 +81,7 @@ machine_init_ex(int m)
 
 	/* Reset the memory state. */
 	mem_reset();
-	smbase = is_486_org ? 0x00060000 : 0x00030000;
+	smbase = 0x00030000;
 
 	lpt_init();
     }