bug#43866: 26.3; italian postfix additions

[Francesco Potortì]

Francesco> I would not include c= and C=.  I would not include e= either.  These
Francesco> things are very annoying unless they are really useful, so better 
just
Francesco> include what's really needed and nothing more.

Robert:
>> The advantage of e= is that (on a US-type keyboard at least) it
>> doesnʼt involve any modifiers. But then again adding it would increase
>> the chances of someone typing it by mistake.

Mattias:
>As you noted, e= is already in latin-postfix. It seems odd to require
>E= in one mode and e= in another. It makes more sense for
>italian-postfix to be a subset of latin-postfix, so that an Italian
>user who needs foreign letters can switch without relearning
>composition pairs. 

I once tried using latin-postfix and I soon stopped, as it creates many
more artifacts that you don't want than ones you want.  Having a lowcase
e for making the euro sign is just one more reason why I wouldn't use
latin-postfix.

If the agreed-upon solution is to put 'e =' on all European postfix
languages, I think that's better leaving them all as they are now.

If the only blocking issue here is inconsistency with latin-postfix,
then better use 'E =' in place of 'e =' on latin-postfix and adding the
same to all European languages.  The only drawback would be for those
using latin-postfix, but after my experience using it, I don't think it
is really used in practice.