This prevents a wrong position of the dialog when there is a different
scroll position like on an URL with fragment, for example
Special:Version?setlang=de#Installed_software
Change-Id: Ic10c6b13461a259d87fd43a718acdd1421193b6c
setlang will now display a dialog to confirm with the user that
they would like to change their interface language. The preferred
language will only be updated if the user confirms.
The dialog will be displayed if the setlang parameter is present in
the query string and,
* A user is logged in, and their preferred language is not the same
as the one passed via setlang.
* For an anonymous user if the wgULSAnonCanChangeLanguage is true,
and the current interface language is not the same as the one
passed via setlang.
Bug: T63115
Change-Id: I882297d99a594fd82fd0aec3b4664e8bfd1eac3a
