bug#43866: 26.3; italian postfix additions

[Robert Pluim]

>>>>> On Thu, 8 Oct 2020 17:23:35 +0200, Mattias Engdegård <mattiase@acm.org> 
>>>>> said:

    >> E= -> €
    >> 
    >> Typewriter-style italian characters. 

    Mattias> If they really are typewriter-style, wouldn't C= make more sense? 
E overstruck with = would just be a smudgy mess even if typed on a beautiful 
Olivetti.

    Mattias> Both C= and E= seem to work as X11 compose pairs. We could include 
both.
    Mattias> That is, c=, C=, e=, E=, and c==, C==, e==, E== as the literal 
cases.

C= would make more sense, but E= (and of course =E for prefix input
methods) is more mnemonic. I can never remember how to type € on a mac
because itʼs not on something obvious like Option-E.

Thereʼs precedence from C-x 8 * as well, which uses E (though perhaps
it should have 'e' as well).

And for total coverage, we *must* add 'C-x 8 2 0 a c' ;-)

Robert
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