How to set a translatable slogan per domain?

Extracted from http://drupal.org/node/1513466

This is now possible with the latest versions of variable and i18n:

• Download latest module versions: variable 2.5, i18n 1.13, domain_variable 1.1.
• Disable domain_conf module if enabled; enable domain_variable_i18n and dependencies.
• Select multilingual variables on admin/config/regional/i18n/variable
• Select domain variables on admin/structure/domain/variables
• Uncheck "Override site name with name of domain" in admin/structure/domain/settings
• Change, e.g. site_slogan variable, …

Note that there is no migration path from the domain_conf module yet (see #1593548: Migration path from domain_conf).