API: Handle "special" options in action=options

There are certain preferences, such as realname and emailaddress, that
are handled specially in Special:Preferences and are not accessible by
User::getOptions or User::setOptions. But action=options was allowing
a 'dummy' version to be set in User::setOptions.

Change-Id: I4c1b3d8e1eae9520228d7b6da9c41ada80f7c387
Merge "API: Handle "special" options in action=options"