FM-TOWNS: Enable aspect ratio correction

[fac]

This is a feature request i found in the tracker (here). Unfortunaly it's not assigned.

I found this soluction the best (for the titles that don't use the bottom 40 lines):

There are two possible "solutions" to the whole issue, I
think:
1) ...
2) Try to cut down the game to 320x200. In the case of ZakTowns, that would imply the game inventory needs to be restricted in size, probably the same for Indy3.

What i want to add is this: Maybe this option could added to ScummVM as a command line parameter (only for 320x240 games). That way it could be tested to see if it's possible to play with such option turned on (At least Loom should be, because it has no inventory).