Add emulation of IBM PS/1 Model 2121.

As part of this :
- FDC Specify command now completes immediately
- Implemented keyboard system flag status
- Added ability to remap 384kb reserved memory to above extended memory

src/fdd.c

@@ -181,3 +181,13 @@ int fdd_get_type(int drive)
 {
 	return fdd[drive].type;
 }
+
+int fdd_is_525(int drive)
+{
+        return drive_types[fdd[drive].type].flags & FLAG_525;
+}
+
+int fdd_is_ed(int drive)
+{
+        return drive_types[fdd[drive].type].flags & FLAG_HOLE2;
+}