Make openbtUnit raunparam mutable instead of using a copy of runparams

in latexParagraphs()

The latter results in output stream encoding errors.

src/OutputParams.h

@@ -207,7 +207,7 @@ public:
 
 	/** Whether a btUnit (for multiple biblographies) is open.
 	 */
-	bool openbtUnit;
+	mutable bool openbtUnit;
 
 	/** Process only the children's aux files with BibTeX.
 	 *  This is necessary with chapterbib.

src/output_latex.cpp

@@ -1259,10 +1259,9 @@ void TeXOnePar(Buffer const & buf,
 void latexParagraphs(Buffer const & buf,
 		     Text const & text,
 		     otexstream & os,
-		     OutputParams const & runparams_in,
+		     OutputParams const & runparams,
 		     string const & everypar)
 {
-	OutputParams runparams = runparams_in;
 	LASSERT(runparams.par_begin <= runparams.par_end,
 		{ os << "% LaTeX Output Error\n"; return; } );