4.16 Babel

<..0,32,4 babel..>
 <.0,32,4 babel.def.>
 \ifx \@begindocumenthook\:UnDef\else
    \:CheckOption{new-accents}     \if:Option \else
       \def\:temp{russian}\ifx \languagename\:temp
          <.russian.>
       \fi
 \fi\fi
-_-_-

We had also \append:def\@begindocumenthook{\HLet\"|=\ddot} in babel. It gets russian and brazil into infinite loop. Why it was inserted.

<..russian..>
 \Configure{accent}\"\ddot{A{A}E{E}I{I}O{O}U{U}Y%
            {Y}a{a}e{e}i{i}\i{i}o{o}u{u}y{y}{e}{}{34}}
    {\a:accents{uml}{#1}}
    {\def\:temp{>}\def\:tempa{#2}\ifx \:temp\:tempa\HCode{}%
     \else \def\:temp{<}\ifx \:temp\:tempa\HCode{}%
     \else \b:accents{uml}{#1}{#2}\fi\fi}
-_-_-