Fix critical markup errors.

Doc/lib/liblogging.tex

@@ -897,7 +897,7 @@ the base message ID in \code{win32service.pyd}.
 \end{methoddesc}
 
 
-\begin{classdesc}PlaceHolder{logger}
+\begin{classdesc}{PlaceHolder}{logger}
 
 \class{PlaceHolder} instances are used in the \class{Manager} logger
 hierarchy to take the place of nodes for which no loggers have been defined
@@ -913,7 +913,7 @@ Add the specified \var{logger} as a child of this placeholder.
 
 \end{methoddesc}
 
-\begin{classdesc}RootLogger{level}
+\begin{classdesc}{RootLogger}{level}
 
 A root logger is not that different to any other logger, except that it must
 have a logging \var{level} and there is only one instance of it in the