I added the plural form support (see a corresponding ticket here:
https://bugs.launchpad.net/zope.i18n/+bug/161985) in a separate branch:
https://code.launchpad.net/~thomas-massmann/zope.i18n/plural. This code
was mainly implemented during the 2012 Plonekonf in Munich.
It is already in "production" since 3 months in a project I'm developing
right now. Please note that zope.i18nmessageid needs to be taken from
this branch to work:
Extracting plural messages is supported by xgettext by default. Zope
tools like i18nduder have to be adjusted (they don't support ungettext
right now). I already adjusted lingua by Wichert Akkerman
(https://github.com/tmassman/lingua) - the pull request is still open.
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