[i18n] Allow for argument swapping

Hello,

when looking into a wrong translation I found the following root cause:

The string “Display at the %s of %s” on line 645 of addtoany.admin.php contains two string placeholders. These might be in a different order in other languages. Please add position specifiers to the placeholders (i.e. “Display at the %1$s of %2$s”) and add a description for translators.

Using the placeholders in the translation only, issues a warning as the placeholders differ from the original string.

Thanks,
Andreas