Add markup for True/False. Will backport

Doc/lib/libpprint.tex

@@ -118,7 +118,7 @@ were added]{2.4}
 \begin{funcdesc}{isreadable}{object}
 Determine if the formatted representation of \var{object} is
 ``readable,'' or can be used to reconstruct the value using
-\function{eval()}\bifuncindex{eval}.  This always returns false for
+\function{eval()}\bifuncindex{eval}.  This always returns \code{False} for
 recursive objects.
 
 \begin{verbatim}
@@ -176,10 +176,10 @@ objects don't need to be created.
 \begin{methoddesc}[PrettyPrinter]{isreadable}{object}
 Determine if the formatted representation of the object is
 ``readable,'' or can be used to reconstruct the value using
-\function{eval()}\bifuncindex{eval}.  Note that this returns false for
+\function{eval()}\bifuncindex{eval}.  Note that this returns \code{False} for
 recursive objects.  If the \var{depth} parameter of the
 \class{PrettyPrinter} is set and the object is deeper than allowed,
-this returns false.
+this returns \code{False}.
 \end{methoddesc}
 
 \begin{methoddesc}[PrettyPrinter]{isrecursive}{object}
@@ -199,7 +199,7 @@ object to be presented.  The second is a dictionary which contains the
 context (direct and indirect containers for \var{object} that are
 affecting the presentation) as the keys; if an object needs to be
 presented which is already represented in \var{context}, the third
-return value should be true.  Recursive calls to the \method{format()}
+return value should be \code{True}.  Recursive calls to the \method{format()}
 method should add additional entries for containers to this
 dictionary.  The third argument, \var{maxlevels}, gives the requested
 limit to recursion; this will be \code{0} if there is no requested