Fix: FDISK not working on korean MSX computers

[Konamiman]

The problem (visible at least in the Daewoo CPC-400) is that the CHPUT routine is supposed to not modify the IX and IY registers, but in this computer it does since it does an inter-slot call to an internal slot (presumably to handle korean characters); this causes the PRINTF routine used by FDISK to crash.

Additionally, a small hack is added to print one less "-" character in the upper and lower rulers when that inter-slot call is performed, otherwise the FDISK screen isn't printed properly (it introduces an additional line break for some reason).

Closes https://github.com/Konamiman/Nextor/issues/100