bug#36717: 25.3; greek.el: deprecated vowel+oxia combinations should be replaced with vowel+tonos counterparts

[Robert Alessi <alessi@robertalessi.net>]

As of 2016, the latest versions of Unicode (as of 2016) have now
formally deprecated and removed the vowel+oxia combinations from the
Greek extended range, leaving only the vowel+tonos from the basic Greek
and Coptic range.

As a result of this deprecation, the sixteen characters found in
greek.el (Quail package for inputting Greek) that use extended
codepoints should be replaced with those that use basic codepoints.  All
affected characters can be found here:
-->
https://wiki.digitalclassicist.org/Greek_Unicode_duplicated_vowels#Affected_characters

Although most Unicode Greek fonts display both versions identically, in
some cases, not using basic codepoints can break advanced features such
as alternate forms in Greek script.  To take an example, if some feature
is supposed to distinguish between regular and `curly' *beta* (β/ϐ) so
as to print the `curly' shape if the *beta* is found in medial position,
the substitution will succeed in βάρβαρος, but fail in λάβρος just
because of the extended codepoint of ά that is used by `greek.el`.

Best,

Robert

---------------------------------------------------------------
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-- 
Robert Alessi
CNRS UMR 8167 «Orient & Méditerranée» (Paris)