Allow full qualified language names (BCP47)

[Omikhleia]

Currently we "normalize" languages to a 2-letter code.

Whatever happens on the SILE front for sile-typesetter/sile#1641

• Relevant shims are in place in silex.sile
• Smartquotes uses them (feat: Support qualified BCP47 languages smartquotes.sile#6, Full language qualified name support smartquotes.sile#1)

Let's rely on silex too, and remove the normalizeLang workarounds we have here and there in the code.

So for instance fr and fr-CH get both correct smartquotes and still load correct hyphenation patterns etc.

[Omikhleia]

Djot

{lang=es}
"Es 'muy' difícil"

{lang=es-MX}
"Es 'muy' difícil"

{lang=fr}
"Un 'bon' essai"

{lang=fr-CH}
"Un 'bon' essai"

Current:

[Omikhleia]

With just removing the normalizeLang hacks:

With SILE complaints:

! Unable to load language feature support (e.g. hyphenation rules) for es-MX: module 'languages.es-MX' not found at es.dj:0:0: in \language[main="es-MX"]
! Unable to load localized strings (e.g. table of contents header text) for es-MX: module 'i18n.es-MX' not found at es.dj:0:0: in \language[main="es-MX"]
! Unable to load language feature support (e.g. hyphenation rules) for fr-CH: module 'languages.fr-CH' not found at es.dj:0:0: in \language[main="fr-CH"]
! Unable to load localized strings (e.g. table of contents header text) for fr-CH: module 'i18n.fr-CH' not found at es.dj:0:0: in \language[main="fr-CH"]

[Omikhleia]

Relying on silex

And no complaints.