Don't use plural forms without specific numbers

[Axel Hecht]

There are a handful of languages which use the same grammatical form for 1 and, say, 11.

If you're using gettext plurals for a message that doesn't specify the number, you get

"Fix the following error." when there are actually 11 errors down the line.

Example would be ​https://github.com/django/django/blob/master/django/contrib/admin/locale/en/LC_MESSAGES/django.po#L427

#: templates/admin/change_form.html:44 templates/admin/change_list.html:67
#: templates/admin/login.html:17
#: templates/admin/auth/user/change_password.html:27
#: templates/registration/password_change_form.html:20
msgid "Please correct the error below."
msgid_plural "Please correct the errors below."
msgstr[0] ""
msgstr[1] ""

[Axel Hecht]

Example plural rule for reference, Lithuanian uses:

<pluralRules locales="lt">

<pluralRule count="one">n mod 10 is 1 and n mod 100 not in 11..19</pluralRule>
<pluralRule count="few">n mod 10 in 2..9 and n mod 100 not in 11..19</pluralRule>

</pluralRules>

[Marc Egli]

I fixed this by using two separate strings.
​https://github.com/frog32/django/commit/8b10363e08e4404a0023da46baee80f2efcb00b5

There is a post on the i18n mailing list about this:
​https://groups.google.com/forum/?fromgroups#!topic/Django-I18N/Ltt4ljM4WpM

I'll squash these two commits together and file a pull request if no one has problems in their translation.

[Claude Paroz <claude@…>]

In b3bccce1a09aae6dfb2eba7f77d3f373f03d8e0c:

Fixed #20455 -- Do not use ngettext for undefined plurals

Using two separate translation strings instead of gettext plural when
there is no reference to the number in the translated string. This
prevents some translations like Russian and Latvian to use the singular
form for 11 or 21.