Modify SLF800* in order to support different keyboard layouts

[giomba]

We want to support the following keyboard layouts:

• US: English (because it's widespread and well-known
• IT: because me and other Italian contributors of the emulator use it
• FR: because this actually is a French computer

[giomba]

Here is a "good enough" (I hope) SLF for the Italian layout (rename file as SLF80037.COM and put it inside the CP/M disk).

SLF80037.IT.TXT

Decisions:

• it maps square brackets [ and ] with the right ALT key modifier (it feels very natural if you're using an Italian ISO keyboard); same for @ and #
• it maps curly brackets { and } to ALT+7 and ALT+0, which feels a bit unnatural, but that's an alternate way of typing these gliphs on an Italian keyboard. The ALT+SHIFT way requires two modifiers, and this is not supported by the Sanco's software - and the emulator doesn't even try to hide it
• it maps the backtick and ~ with ALT+' and ALT+ì, which is the natural way, if you have used an Italian keyboard to program on Linux in the past 30 years
• it maps the extra ISO key (that European keyboards have) to type < and > in the Italian layout

In order to map this last key, I added a patch for the emulator to support the extra ISO key (see GLGPrograms/ceda-cemu@a33406d )

Accented letters have no representation in the original ASCII table, so the Sanco does not support them, so, I mapped accented letters (à, è, é, ì, ò and ù) simply to their non-accented counterpart.
I left ç, ° and § out because they are not ASCII, and also who does use them anyway?

[giuliof]

Done with #3